Mineralogical Characteristics Research Articles

Mechanical, microstructural, and thermal characterization of geopolymer composites with nano‐alumina particles and micro steel fibers

AbstractCement production is responsible for 5%–7% of global CO2 emissions, highlighting the need for sustainable alternatives like geopolymer composite (GCOMP) to meet the growing demand for concrete. This study investigates the mechanical, microstructural, and thermal properties of GCOMP by incorporating nano‐alumina (n‐alumina) and MSF (MSF). The n‐alumina content was varied at 1%, 2%, and 3% by weight of the mix, while the MSF content remained fixed at 0.5% by weight. Thermal characterization was conducted up to 800°C. The performance of GCOMP blends with n‐alumina was compared to a control blend consisting of only 0.5% MSF. Various mechanical properties were evaluated for all GCOMP blends. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier‐transform infrared spectroscopy (FTIR). Thermogravimetric and differential thermal analysis were performed up to 800°C for the thermal analysis of the GCOMP mix. The results indicate that the optimal mechanical properties were achieved with 2% n‐alumina (compressive and flexural strength increased by 35.65% and 77.7%, respectively). Additionally, the incorporation of n‐alumina improves the interfacial zones and results in a denser structure. GCOMP mortars portrayed a mass loss between 25°C and 250°C, with a marginal mass loss occurring between 250°C and 715°C. No mass loss was observed between 715°C and 800°C. The MSF‐reinforced GCOMP mortars experienced an ultimate mass loss of approximately 12%, with the MSF showing negligible influence. The addition of n‐alumina particles to MSF‐reinforced GCOMP resulted in the development of stronger samples characterized by the presence of C–S–H, calcium aluminate oxide hydroxide, and quartz.

Geochemistry of fluoride mobilization in the hard-rock aquifers of central India: Implication for fluoride-safe drinking water supply

Globally, groundwater contamination by fluoride (F−) is a threat to the safe drinking water supply. Nevertheless, our understanding of the geochemical processes of F− mobilization to the groundwater by linking groundwater and aquifer material chemistry is limited. We therefore characterized that in the hard-rock aquifers of Central India, an area that has not been investigated thoroughly despite the known severity of the problem. Exploratory drilling of boreholes (n = 45) and lithostratigraphic modeling identified weathered basalt, vesicular basalt, fractured basalt, sandstone of Lameta, and fractured granite as major aquifers in the study area. The groundwater contamination by F− (concentration >1.5 mg/L) mainly occurred at depths >35 m bgl (at elevations <500 m amsl) of the fractured basalt and fractured granite aquifers, while samples collected from the shallow basalt, sandstone of Lameta, and shallow granite were mostly safe. The F− contamination of groundwater was primarily governed by the chemical evolution of groundwater along the flow path. Solute mass balance in groundwater, in conjunction with the mineralogical characterization of the aquifer materials, suggests that weathering of silicate and carbonate minerals was the dominant form of mineral dissolution in aquifers, which consumed dissolved CO2 along the flow path and resulted in an alkaline pH (>8) in groundwater of the deeper aquifers. The mobilization of F− in the groundwater could primarily be attributed to the ion exchange between OH− in water and structural F− in fluorapatite and F-bearing mica/amphibole. By assessing water quality and aquifer properties, this study suggests that primarily, the sandstone of Lameta and weathered and vesicular basalts can be targeted for F-safe drinking water supply in the study area. Targeting shallow aquifers can be an option for F-safe drinking water supply in other affected areas with similar geological and environmental settings.

Performance investigation of the artificial aggregate by integrally recycling incineration bottom ash and fly ash

The potential expansion risks caused by the reaction of metallic aluminum and glass particles in incineration bottom ash (IBA) in high-alkalinity environments limit its use as an aggregate in concrete applications. This study aims to develop artificial aggregates (AAs) by integrating IBA with a low-alkalinity binder comprising incineration fly ash (IFA) and blast furnace slag (GGBS). The synergetic effects of using IBA with IFA-GGBS binders in AAs are investigated and compared to integrating IBA with IFA-OPC binders. The impacts of IFA and IBA contents on physico-mechanical properties and mineralogical characteristics of AAs are also assessed. The results show that AAs achieve a loose bulk density ranging from 890 to 1072 kg/m3, with the highest strength of 5.7 MPa recorded for GGBS-based aggregates with 40 % IBA. The pozzolanic reaction of GGBS-IFA contributes to a robust binder that facilitates interlocking within the system. The relatively low alkalinity associated with the pozzolanic reaction between GGBS and IFA suppresses the potential expansion reaction, ensuring the safe application of AAs in concrete. Moreover, the internal curing of GGBS-based AAs and their interaction with the cement matrix densify the microstructure of the interface transition zone, resulting in excellent compressive strength of AAs-contained concrete (>45 MPa), which surpasses that of conventional concrete.

Chemical and mineralogical characterisation of Duguri Galena (Bauchi State, Nigeria)

This paper presents a detailed study of Galena samples' chemical and mineralogical properties collected from the Duguri area in Bauchi State, Nigeria. The sample for the research was sourced from Duguri town, Bauchi State, Nigeria. The sourced sample underwent comminution, homogenization, and sampling using the Coning and Quartering method followed by the Jones Riffle sampling method. Chemical analysis results of the crude ore sample showed the presence of Lead oxide (PbO) at an assay of 36.827 %, with Silica as the major gangue mineral present at 45.823 %. The other compounds present in the ore are ZnO (9.656 %), Fe2O3 (8.290 %), Al2O3 (3.409 %), TiO2 (1.072 %), WO3 (0.312 %), and AgO (0.001 %). Mineralogical Characterisation using XRD revealed the phases present in the ore as; Galena (47 %), Cerussite (19.0 %), Quartz (18.8 %), and Gratonite (15 %), hence confirming that the soured ore was Galena (PbS). SEM/EDS results showed the morphology of the sourced sample, containing Lead with other impurities in their quartz form within the ore matrix, with the presence of other elemental constituents (Si, C, and O). Keywords: Galena, Chemical analysis, Mineralogical characterisation, Duguri area, Bauchi State, Nigeria.

Mineralogy and Geochemistry of Rare Earth Elements in Carboniferous-Permian Coals at the Eastern Margin of the Ordos Basin.

This article used Carboniferous-Permian coals from the Jungar, Hedong, and Weibei Coalfields in the east of the Ordos Basin as research samples. Characteristics of coal quality, petrology, mineralogy, and geochemistry were analyzed by proximate analysis, inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy, X-ray diffraction analysis, scanning electron microscopy-energy spectrum analysis, and incident light microscope. The enrichment regulations, distribution patterns, and occurrences of REY (rare earth element and yttrium) in coal under different geological conditions were compared. Geological significance and the influence of REY were then discussed. The average REY of Permian coal in the eastern margin of the basin is 127.9 μg/g, CC = 1.87, and the average REY of Carboniferous coal is 117.49 μg/g, CC = 1.72, which are within the normal enrichment range. The inorganic affinity of REYs in the study area is strong and mainly occurs in clay minerals and detrital phosphates and correlates well with LREY. The Permian coal sedimentary environment is more oxidized than the Taiyuan formation, and the Carboniferous coal sedimentary environment is noticeably more affected by marine water. With an increasing degree of coalification, the concentration of rare earth elements (REE) in high-rank coal vitrinite is lower than that in inertinite. In contrast, the concentration of REEs in low-rank coal is the opposite. This is because the oxygen-containing functional groups that can combine with REEs in vitrinite reduce significantly, resulting in the loss of trace elements into other forms. The provenance of the northern and central regions of the study area is mainly sedimentary rocks, granite, alkaline basalt, and continental tholeiite, while the southern region is mainly granite and sedimentary rocks.

Sustainable valorization of mining waste: Phosphate sludge repurposing for advanced ceramic production

Managing the vast quantities of waste constantly generated by mining activities is one of the major environmental and economic problems facing mankind today. Fluorapatite is separated from the associated gangue minerals by a series of crushing and screening, washing, and flotation processes. These processes produce a significant amount of phosphate sludge, which is stored on the mine site in drift rock and large surface ponds. One possible environmental option is to reuse it as an alternative raw material in ceramics and building materials. Consequently, two phosphate sludges from two different Moroccan towns, Youssoufia and Khouribga, were studied. Due to the complexity of these raw materials resulting from long geological processes, in-depth physical, chemical, mineralogical, and thermal characterization is required. Dry compressed powder pellets were sintered at 900 °C, 1000 °C, and 1100 °C for 2 h. The study focuses on the effect of sintering temperature on mineralogical transformations and ceramic properties such as apparent porosity, water absorption, and mechanical strength. At 1100 °C, a slight increase in density was observed for both phosphate sludges. Water absorption was reduced by 2.51 % in both sludges for pellets sintered at 1100 °C compared to those sintered at 900 °C. Mechanical strength improved significantly, with an increase of about 60 % for samples sintered at 1100 °C, recording 227 N for Youssoufia sludge and 247 N for Khouribga sludge. This work has provided new data on the physical, chemical, mineralogical, and thermal changes in ceramics as the sintering temperature increases. These data will be useful for the manufacture of high-value ceramics.

Critical Raw Materials Supply: Challenges and Potentialities to Exploit Rare Earth Elements from Siliceous Stones and Extractive Waste

Critical raw materials (CRMs) supply is a challenge that EU countries have to face, with many thinking about domestic procurement from natural ore deposits and anthropogenic deposits (landfills and extractive waste facilities). The present research focuses on the possibilities linked to the supply of CRMs and the potential for exploiting rare earth elements (REEs), investigating a large variety of extractive waste and siliceous rocks in the Piedmont region (Northern Italy). Indeed, the recovery of REEs from the extractive waste (EW) of siliceous quarries and other siliceous ore deposits can be a valuable way to reduce supply chain risks. Starting with a review of the literature on mining activities in Piedmont and continuing with the sampling and geochemical, mineralogical, petrographic, and environmental characterization of EW facilities connected to siliceous dimension stones, of kaolinitic gneiss ore deposits, and of soils present near the investigated areas, this study shows that the degree of REEs enrichment differs depending on the sampling area (soil or EW) and lithology. The concentration of REEs in the EW at some sampling sites fulfils the indicators of industrial-grade and industrial recovery; the high cumulative production and potential market values of EW and the positive recovery effects through proven methodologies indicate a viable prospect of REE recovery from EW. However, REE recovery industrialization faces challenges such as the difficulty in achieving efficient large-scale recovery due to large regional differences in REE abundance, the mismatch between potential market value and waste annual production, etc. Nonetheless, in the future, EW from dimension stone quarries could be differentially studied and reused based on the enrichment and distribution characteristics of trace elements. The present paper shows investigation procedures undertaken to determine both CRMs potentialities and environmental issues (on the basis of literature data employed to select the more-promising areas and on sampling and characterization activities in the selected areas), together with procedures to determine the waste quantities and tentative economic values of REEs present in the investigated areas. This approach, tested on a large area (Piedmont region), is replicable and applicable to other similar case studies (at EU and non-EU levels) and offers decision makers the possibility to acquire a general overview of the potential available resources in order to decide whether and where to concentrate efforts (including economic ones) in a more detailed study to evaluate the exploitable anthropogenic deposits.

Soil‐vegetation interplay in a Holocene toposequence at Torres del Paine National Park, southern Andes, Chile

AbstractChile's Torres del Paine National Park (TPNP) is one of the most impressive landscapes in southern Patagonia, with unique natural elements on the edge of the southern ice field, where knowledge of soils and ecological relationships is nonexistent. Therefore, the objective of this study was to determine the chemical, physical, mineralogical, and micromorphological characteristics of Holocene soils along a local toposequence representing the main vegetation types of the TPNP. The morphological, chemical, physical, and mineralogical properties of 12 soil profiles were studied and classified according to Soil Taxonomy. Coevolution of vegetation and soil taxa is clearly evident since glaciation, with podsolization under austral Nothofagus pumilio forests leading to the development of spodosols, while paludization in local depressions with Nothofagus forests allowed the formation of histosols. Slopes covered with loess and tephra led to the formation of Andisols with shrub vegetation. Predominant parent materials include till from Late Quaternary advances of southern Andean ice, Pleistocene loess, and volcanic ash from surrounding Chilean volcanoes. The parent materials were strongly influenced by Late Quaternary climatic and landscape changes following the retreat of the Last Glacial Maximum in southern Patagonia, resulting in erosional and depositional conditions (windblown loess, fluvial glacial deposits, and moraines). Stable landforms show the influence of allochthonous volcanic ash shaping Andean features, combined with the accumulation of organic matter in hydromorphic soils. Three main groups of soils have been identified: loess‐rich soils, organic‐rich soils, and poorly developed soils. The latter show low fertility related to recent landforms on different substrates ranging from till, rocky slopes, talus, or glacial deposits. In high mountain regions under periglacial conditions, cryoturbation features indicate seasonal frost–thaw cycles without current permafrost. The diversity of soil orders in the mountains of southern Patagonia is comparable to similar environmental conditions and latitudes in the Northern Hemisphere. However, the andic properties due to volcanic ejecta inputs, as well as organic‐rich soils at low altitudes of bottom valleys, are typical features of the soils at TNTP.

Assessment of the soil utilization potential of vanadium-titanium magnetite tailings based on a chemical, biological, and mineralogical characterization

Assessment of the soil utilization potential of vanadium-titanium magnetite tailings based on a chemical, biological, and mineralogical characterization

Impact of clay minerals on reservoir sandstone properties: comparative study in Colombian eastern cordillera and middle Magdalena valley basins

The aim of this study is to examine how mineralogy influences the petrophysical properties, particularly porosity and permeability, of potential sandstone reservoirs in Colombia. It seeks to comprehensively understand how the presence of clay minerals impacts the overall quality of hydrocarbon reservoirs in the country. Samples of sandstones from reservoirs at various outcrops in the Eastern Cordillera and Middle Magdalena Valley basins were collected. Detailed analysis of mineralogy and petrographic characteristics of the samples was conducted through various analytical techniques such as transmitted light microscopy, X-ray diffraction, and scanning electron microscopy. Porosity and permeability were measured using automated permeametry and porosimetry equipment. The predominant composition of the analyzed reservoir rocks comprises quartz (45-50%), feldspar (35-40%), and clays (10-20%). These rocks were categorized into two distinct groups based on their permeability (K) and porosity (Φ), ranging from 0.009 to 29.220 mD and 1.88 to 20.75%, respectively. The presence of illite correlated with a reduction in both porosity and permeability, highlighting its negative impact on reservoir quality. Conversely, an elevated concentration of kaolinite was associated with favorable porosity and permeability. Samples with feldspar sericitization demonstrated inferior hydrocarbon storage quality. This study provides a deeper understanding of how mineralogy affects the petrophysical properties of sandstone reservoirs in Colombia. These findings are crucial for guiding exploration and production strategies in the Colombian oil industry, especially in challenging geological environments like those studied.

Textural and mineralogical characteristics of sediments originated from salt domes in the northern part of the Hormuz Strait

Textural and mineralogical characteristics of sediments originated from salt domes in the northern part of the Hormuz Strait

A supervised multiclass framework for mineral classification of Iberian beads.

Research on personal adornments depends on the reliable characterisation of materials to trace provenance and model complex social networks. However, many analytical techniques require the transfer of materials from the museum to the laboratory, involving high insurance costs and limiting the number of items that can be analysed, making the process of empirical data collection a complicated, expensive and time-consuming routine. In this study, we compiled the largest geochemical dataset of Iberian personal adornments (n = 1243 samples) by coupling X-ray fluorescence compositional data with their respective X-ray diffraction mineral labels. This allowed us to develop a machine learning-based framework for the prediction of bead-forming minerals by training and benchmarking 13 of the most widely used supervised algorithms. As a proof of concept, we developed a multiclass model and evaluated its performance on two assemblages from different Portuguese sites with current mineralogical characterisation: Cova das Lapas (n = 15 samples) and Gruta da Marmota (n = 10 samples). Our results showed that decisión-tres based classifiers outperformed other classification logics given the discriminative importance of some chemical elements in determining the mineral phase, which fits particularly well with the decision-making process of this type of model. The comparison of results between the different validation sets and the proof-of-concept has highlighted the risk of using synthetic data to handle imbalance and the main limitation of the framework: its restrictive class system. We conclude that the presented approach can successfully assist in the mineral classification workflow when specific analyses are not available, saving time and allowing a transparent and straightforward assessment of model predictions. Furthermore, we propose a workflow for the interpretation of predictions using the model outputs as compound responses enabling an uncertainty reduction approach currently used by our team. The Python-based framework is packaged in a public repository and includes all the necessary resources for its reusability without the need for any installation.

Biotic and abiotic processes in Ediacaran spheroid formation

Organic-rich shales from the uppermost Doushantuo Fm. (South China) record one of the most negative carbonate carbon isotopic excursions in Earth’s history, known as the Shuram excursion, and contain meter to micro-size spheroids. In this study, we use Raman and energy dispersive spectroscopy to identify and describe the most common diagenetic spheroids to refine our understanding of the profound perturbations of the carbon cycle and the evolution of pore fluid chemistry imprinted in the sedimentary Precambrian record, especially in the late Ediacaran. The presence of 13C-depleted carbonate concretions or organic matter (OM) enclosed by lenticular dolomitic structures within the host shale unit suggests OM remineralisation and anaerobic oxidation, resulting in authigenic carbonate precipitation during the earliest stages of sediment diagenesis. Other mineralogical features, however, point to high levels of primary production, such as apatite bands that host spheroidal microfossils with highly fluorescent quartz and OM within abiotic concretions. These observations highlight the importance of considering co-occurring biotic and abiotic processes in explaining the formation of diagenetic spheroids in ancient sedimentary environments. From an astrobiology perspective, the interplay of biotic and abiotic processes reflects the complexity of early life systems and the environments that may exist on other terrestrial planets. Understanding the signatures of biotic and abiotic interactions in the Doushantuo Fm. is crucial for identifying potential biosignatures in extraterrestrial materials, thereby enhancing our understanding of life’s universality and adaptability in diverse and extreme environments.

Lithological and mineralogical characteristic of the bottom sediments in the areas of ice scouring in the south-western Kara Sea

Lithological and mineralogical characteristic of the bottom sediments in the areas of ice scouring in the south-western Kara Sea

Investigation of Cd(II) removal mechanism during biogenic Mn(II) oxidation by Cladosporium sp. XM01

Biogenic Mn oxides (BMOs) represent the most prevalent natural form of Mn oxides, having a significant influence on the biogeochemical cycling of Cd in the environment. The surface reactivity of BMOs is intricately linked to their structural characteristics. However, there remains a scarcity of knowledge regarding the structural disparities of BMOs during their formation in the context of heavy metal removal. This study investigates the fine mineralogical characteristics of three BMOs formed by the Mn-oxidizing fungus Cladosporium sp. XM01 during cultivation, namely immature BMO (Imm-BMO), low mature BMO (Low-BMO), and high mature BMO (High-BMO), and their adsorption mechanism for Cd(II). Analysis of Mn K-edge X-ray absorption fine structure indicated three BMOs exhibit a hexagonal birnessite structure with interlayer Mn(II/III), and Imm-BMO (48.6 %) exhibits a higher proportion of Mn(II/III) components compared to Low-BMO (14.4 %) and High-BMO (13.9 %). The results suggested a gradual decrease in Cd(II) adsorption capacity, following the order of Imm-BMO, Low-BMO, and High-BMO. Conversely, Cd(II) showed higher fixation capacity on Low-BMO (56.2 %−63.1 %) and High-BMO (64.4 %−70.6 %) compared to Imm-BMO (45.4 %−52.6 %), indicating an opposite trend in Cd(II) fixation. Specifically, the enhanced Cd(II) fixation performance during BMOs formation can be attributed to the availability of more vacancies and interlayer spaces for Cd(II) occupation and retention, respectively. Additionally, compared with pH 7.5, pH 5.5 was found to be more conducive to Cd(II) fixation on BMOs, attributed to the increased availability of more vacancies. Overall, this study enhances our understanding of the structural transformation during BMOs formation and its implication for Cd(II) adsorption behavior.

Radiometric and petrographic characterization of El-Yatima granite: Evaluating radiological risks and mineralogical features

The current investigation aims to assess the potential of El-Yatima granitic pluton as a decorative stone by examining its natural radioactivity and mineralogical elements. Specifically, the study aims to determine the concentrations of radionuclides 40K, 232Th, and 226Ra, perform petrographic analyses, and evaluate the associated radiological risks to determine the safety and usability of the granite in construction and decoration, as well as to assess the potential of these granitic rocks as a safe and effective decorative stone for various applications. It has a 12 km2 surface area of 812 m above sea level. It is situated in the Eastern Central Desert. Its hypidiomorphic texture, medium-to-coarse grain size, and predominant composition of K-feldspars, quartz, and plagioclase are observed, along with minute amounts of muscovite and biotite. By employing NaI (Tl) gamma-ray spectroscopy, the natural radionuclide concentrations of 40K, 232Th, and 226Ra in El-Yatima granitic rocks were ascertained. Additionally, radiological concerns were identified for the materials that were examined. The average concentrations of radionuclides 40K, 232Th, and 226Ra are 178 Bqkg−1, 44 Bqkg−1, and 41 Bqkg−1, respectively. The following are the computed values: 117 Bqkg−1, 0.43, 0.32, 53 nGyh−1, average radium equivalent (Raeq), hazard indices (Hin and Hex) and dose rate (D), respectively. When compared to levels typically indicated, it was discovered that its values were within the worldwide standard. The study's findings could be a starting point for radiometric data for upcoming surveillance and epidemiological research.

Heterogeneity of Organoclay Complexes in Shale Regulates the Generation of Shale Oil.

Organic matter (OM) and clay minerals are important components in shale, which are intimately associated with each other in the form of organoclay complexes. The diverse mineral-OM associations result in varying OM occurrences, which possess distinct hydrocarbon generation potential and ultimately affect the accumulation of shale oil. Therefore, the investigation of the heterogeneity of organoclay complexes is crucial to gaining a comprehensive understanding of the varying exploration potential of shale oil resources. In the present study, shale samples from three intervals in Dongying Depression were collected to investigate the mineralogical and organic characteristics of the organoclay complexes, aiming to explore their impact on the yield and composition of shale oil. Results showed that the smectite gradually converted into illite, which was accompanied by the release of OM from clay mineral interlayers and the desorption of chemically adsorbed OM. The yield and composition of shale oil cannot solely be explained by the OM content and types in the shale. Instead, they are intricately linked to the evolution of minerals and OM occurrence. From the perspective of the heterogeneity of organoclay complexes, despite the abundant OM content in shallower intervals (Es3x), the shale oil formation remains limited due to the low degree of mineral evolution and the stabilization of the adsorbed OM by clay minerals. Consequently, this leads to a higher proportion of resin, which is not conducive to the mobility of shale oil. In contrast, despite the OM content varying slightly in the deeper interval (Es4s), the elevated smectite illitization degree promotes the desorption of OM and its conversion into hydrocarbons. This results in a substantial increase in shale oil formation and a higher proportion of saturates, greatly enhancing the mobility of shale oil. These findings are profoundly significant for understanding shale oil generation and accumulation.

Environmental relevance monitoring and assessment of ochreous precipitates, hydrochemistry and water sources from abandoned coal mine drainage

This study investigated the mineralogical and chemical characteristics of ochreous precipitates and mine water samples from abandoned Upper Carboniferous hard coal mines in an extensive former mining area in western Germany. Mine water characteristics have been monitored and assessed using a multi-methodological approach. Thirteen mine water discharge locations were sampled for hydrochemical analysis, with a total of 46 water samples seasonally collected in the whole study area for stable isotopic analyses. Mineralogical composition of 13 ochreous precipitates was identified by a combination of powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM/EDS). Results showed that abandoned mine drainage was characterized by circumneutral pH, Eh values ranging from 163 to 269 mV, relatively low concentrations of Fe and Mn, and was dominated by HCO3− > SO42− > Cl− > NO3− and Na+ > Ca2+ > Mg2+ > K+. Goethite and ferrihydrite were the dominant precipitated Fe minerals, with traces of quartz, dolomite, and clay minerals. Some metal and metalloid elements (Mn, Al, Si, and Ti) were found in the ochreous sediments. The role of bacteria in the formation of secondary minerals was assessed with the detection of Leptothrix ochracea. The δ18O and δ2H values of mine water plotted on and close to the GMWL and LMWLs indicated local derivation from meteoric water and represented the annual mean precipitation isotopic composition. Results might help to develop strategies for the management of water resources, contaminated mine water, and public health.

Characterization and utilization potential of typical molybdenum tailings in Shaanxi Province, China.

Shaanxi Province is located in the most important molybdenum ore district in the world, but a lot of molybdenum tailings have been released, polluting the environment and wasting resources seriously. Taking eleven tailing samples collected at the main molybdenum tailings ponds in Shaanxi Province as the research object, the physical, chemical, and mineralogical characteristics were studied through scanning electron microscope, X-ray fluorescence, X-ray diffraction, inductively coupled plasma mass spectrometer, and others. The ecological risk and utilization potential of molybdenum tailings were investigated through leaching test, geo-accumulation index, potential ecological risk assessment, and other methods. The results demonstrated that the main chemical and mineralogical composition of various molybdenum tailings in Shaanxi Province is similar, and the predominant mineral composition is muscovite, quartz, microcline, and calcite. The potential ecological risk of heavy metals in six molybdenum tailings is high, while Pb and Cd are the main pollution risk elements. Molybdenum tailings contain considerable amounts of critical minerals with huge potential economic value, and molybdenum tailings with high environmental hazards could be converted into a possible source for critical minerals by recovering the critical minerals and repurposing the secondary tailings as an additive or cement substitute. This study provides an innovative idea for the pollution treatment of molybdenum tailings and indicates the prospect of molybdenum tailings as a secondary source for critical minerals.

Wide-Temperature Characteristics of Additively PBF-LB/M Processed Material Ti6Al4V

Titanium-based alloys are a widely applicable engineering material with high strength, low weight, non-magnetic, and corrosion resistance. At the same time, resistance to low temperatures is declared, which offers the material’s applicability for, e.g., aircraft or ship technology. Additive technologies are part of the industrial spectrum of material processing, especially the Laser Powder Bed Fusion of Metals method for metal alloys, which creates a layered structure of the resulting body. The topology of the internal structure, in relation to the temperature history of the functional environment, influences thermal expansion and the associated functional characteristics. Knowledge of the thermal expansion of printed strength and non-strength functional components and accessories is essential for future applications, especially in environments with high repeatable temperature changes, such as the aerospace industry. This paper presents the results of testing the expansion, mechanical, microstructural, and mineralogical characteristics of Ti6Al4V over the temperature range of −70 to 60 °C using a combination of instrumental techniques such as X-ray diffraction and nanoindentation. It was found that the topological orientations of the printed samples directly influenced the tested properties, e.g., the coefficient of thermal expansion in the direction perpendicular to the printed layers showed approximately 12% lower value compared to the other directions. Due to the progression of the application of the manufacturing method and its applicability within selected industries, the research provides results in a new area, which is supported by the relevant research.