Continuous Precipitation Research Articles

Ageing response and microstructural evolution of biodegradable Zn-1.5Cu-1.5Ag alloy

In this study, the age-hardening response and microstructural evolution of an as-extruded biodegradable Zn-1.5Cu-1.5Ag (wt.%) alloy during ageing at 25 ℃, 100 ℃, 150 ℃ and 200 ℃ are studied. The age-hardening response is generally weak, and the largest hardness increment is observed after ageing at 150 ℃ for 24 h. Discontinuous precipitation (DP) and continuous precipitation (CP) occur competitively during ageing at 150 ℃ or 200 ℃, while only DP is observed during ageing at 25 ℃ or 100 ℃. All the precipitates formed through DP and CP are identified as ε-(Ag, Cu)Zn4 that has a hexagonal structure. Analysis of possible strengthening mechanisms shows that grain boundary strengthening and precipitation hardening contribute to the major part of yield strength in the as-extruded condition. Ageing treatments generate a limited increment in yield strength due to the small difference between the hardness of ε-(Ag, Cu)Zn4 and the Zn matrix and the reduced solid solution strengthening effect. Artificial ageing at 150 ℃ for 48 h effectively improves the stability of the mechanical properties of the as-extruded Zn-1.5Cu-1.5Ag alloy. This process fully depletes the excessive solutes in the supersaturated Zn matrix, ensuring that the alloy maintains consistent mechanical properties when stored at room temperature.

Investigation of the Softening Resistance Behavior and Its Mechanism in Cu-Ni-Si Alloys with Discontinuous Precipitates.

In this study, isothermal annealing experiments were conducted on copper-nickel-silicon alloys containing continuous precipitates (CP) and discontinuous precipitates (DP) to investigate the effects of different types of precipitate phases on the microstructural evolution and softening temperature during annealing, as well as to analyze the differences in softening mechanisms. The experimental results revealed that the softening temperature of the CP alloy, subjected to 75% cold deformation, was 505 °C. In contrast, the DP alloy achieved softening temperatures of 575 °C and 515 °C after 75% and 97.5% cold deformation, respectively. This indicates that the DP alloy exhibits significantly superior softening resistance compared to the CP alloy, attributed to the distinct softening mechanisms of the two alloys. In the CP alloy, softening is primarily influenced by factors such as the coarsening of the precipitate phase, the occurrence of recrystallization, and the reduction in dislocation density. In the DP alloy, the balling phenomenon of the DP phase is more pronounced, and its unique microstructure exerts a stronger hindrance to dislocation and grain boundary motion. This hindrance effect reduces the extent of recrystallization and results in a smaller decrease in dislocation density. In summary, the DP alloy, due to its unique microstructure and softening mechanisms, demonstrates better softening resistance, providing higher durability and stability for high-temperature applications.

Investigating a Century of Rainfall: The Impact of Elevation on Precipitation Changes (Northern Tuscany, Italy)

Precipitation is crucial for water resource renewal, but climate change alters their frequency and amounts, challenging societies for correct and effective water management. However, modifications of precipitation dynamics appear to be not uniformly distributed, both in space and time. Even in relatively small areas, precipitation shows the coexistence of positive and negative trends. Local topography seems to be a strong driver of precipitation changes. Understanding precipitation changes and their relationship with local topography is crucial for society’s resilience. Taking advantage of a dense and long-lasting (1920–2019) meteorological monitoring network, we analyzed the precipitation changes over the last century in a sensitive and strategic area in the Mediterranean hotspot. The study area corresponds to northern Tuscany (Italy), where its topography comprises mountain ridges and coastal and river plains. Forty-eight rain gauges were selected with continuous annual precipitation time series. These were analyzed for trends and differences in mean annual precipitation between the stable period of 1921–1970 and the last 30-year 1990–2019. The relationship between precipitation changes and local topography was also examined. The results show the following highlights: (i) A general decrease in precipitation was found through the century, even if variability is marked. (ii) The mountain ridges show the largest decrease in mean annual precipitation. (iii) The precipitation change entity over the last century was not homogenous and was dependent on topography and geographical setting. (iv) A decrease in annual precipitation of up to 400 mm was found for the mountainous sites.

Evolution of precipitate and its effect on the degradation of impact toughness in a carbon and nitrogen-controlled 316 stainless steel during thermal aging at 650 °C

Impact toughness degradation and microstructure evolution of a carbon and nitrogen-controlled 316 stainless steel during long-term aging at 650 °C for up to 8800 h were investigated. The degradation of impact toughness during aging can be divided into three stages: a rapid decrease during stage I (the first 400 h), a slow decrease during stage II (from 400 to 3200 h), and the stable stage during stage III (up to 8800 h). P enrichment at the M23C6/γ interface is induced by the rejection of P during the formation of M23C6 carbide, and the M23C6/γ interface is preferred location for crack initiation. An increase in the amount of grain boundary M23C6 carbides increases the crack initiation sites, resulting in a rapid decrease of impact toughness during stage I. The ongoing rejection of Ni and Si during the coarsening of M23C6 carbide is beneficial for the nucleation of M6C carbide. The micro-crack initiation at the M23C6/M6C and M6C/γ interfaces is introduced, and a semi-continuous network of M23C6 carbide along grain boundary promotes the crack propagation, leading to a further decrease of impact toughness during stage II. The nearly continuous precipitate morphology is induced through continued growth of grain boundary M23C6 and M6C carbides. The propagation of micro-cracks along the M6C/γ, M23C6/γ, and M23C6/M6C interfaces leads to the mostly intergranular fracture, thus the impact energy tends to be stable during stage III.

Improving mechanical and electrical properties of Cu-Ni-Si alloy via machine learning assisted optimization of two-stage aging processing

Recent studies have shown that synergistic precipitation of continuous precipitates (CPs) and discontinuous precipitates (DPs) is a promising method to simultaneously improve the strength and electrical conductivity of Cu-Ni-Si alloy. However, the complex relationship between precipitates and two-stage aging process presents a significant challenge for the optimization of process parameters. In this study, machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs. Two-stage aging parameters of 400 °C/75 min + 400 °C/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy, resulting in a tensile strength of 875 MPa and a conductivity of 41.43 %IACS, respectively. Such an excellent comprehensive performance of the alloy is attributed to the combined precipitation of DPs and CPs (with a total volume fraction of 5.4% and a volume ratio of CPs to DPs of 6.7). This study could provide a new approach and insight for improving the comprehensive properties of the Cu-Ni-Si alloys.

MLAPI: A framework for developing machine learning-guided drug particle syntheses in automated continuous flow platforms

Recently, machine learning (ML) models are increasingly being used in process analytical technology (PAT) frameworks for pharmaceutical manufacturing. Yet, the applications of ML-integrated PAT frameworks are limited by big data requirements. This work introduces a computational framework to develop data-efficient ML models to guide drug particle synthesis in an automated continuous flow precipitation platform. The framework incorporates classification algorithms to identify feasible (fouling-free) operating regions of the precipitation platform, a multiple-output Gaussian process (GP) regression model to relate key process parameters to the drug particle size, and active learning to optimally generate new data for training and validation of the GP model. The usefulness of the proposed framework is demonstrated on the synthesis of ibuprofen microparticles in an automated flow precipitation platform. We envision that properly trained GP models developed using the proposed framework can be employed to fine tune the drug particle size, targeting desired particle bioavailability and processability.

Precipitation behavior of Pt-rich phase in Au72Pt28 alloy during aging process

Gold–Platinum (Au–Pt) alloy demonstrates considerable promise as a material for spacecraft proof mass, due to its ultra-low magnetic susceptibility. This study systematically investigates the effect of heat treatment on the microstructure evolution, magnetic properties, and mechanical performance of the Au72Pt28 alloy. The results indicate that the Pt-rich phase can be precipitated by discontinuous precipitation (DP) and continuous precipitation (CP) reactions. There is a competition between the two precipitation behaviors of Pt-rich phase, which is closely related to their diffusion path. With increasing ageing time and temperature, the discontinuous precipitates gradually coarsen and extend from grain boundaries into grain interior, while the Pt-rich phase nanoparticles precipitated by CP reaction uniformly distribute in the grain interior. Besides, the volume fraction of Pt-rich phase gradually increases, resulting in the increase of magnetic susceptibility. The coarsening of discontinuous precipitates is the main reason for the decrease in the nanoindentation hardness, and it increases rapidly due to a large number of intragranular Pt-rich phase nanoparticles.

Regulating precipitate characteristics in a rolled AZ80 alloy based on twinning and de-twinning deformation

The effect of twinning and de-twinning on precipitation behavior of a rolled AZ80 alloy has been examined. Results showed that both twinning and de-twinning deformation can promote the precipitation of continuous precipitates. And only dense continuous precipitates can be formed inside twinned and de-twinned regions. The high density crystal defects existing in the twinned and de-twinned regions increase the diffusion rate of solute elements and provide more nucleation sites for precipitation, resulting in a homogeneous and dense distribution of continuous precipitates in these regions. Comparing to direct aging, both post-twinning aging and post-de-twinning aging can remarkably increase the yield strength and peak strength by promoting the precipitation of continuous precipitates. For tension and compression, both direct aging and post-de-twinning aging reduce the strain corresponding to peak strength (εp) and static toughness (UT) to a close level. In contrast, post-twinning aging exhibits little loss in εp and largely increases UT. The strengthening and toughening mechanisms were also discussed in detail.

Using Satellite Observations of Lightning and Precipitation to Diagnose the Behavior of Deep Convection in Tropical Cyclones Traversing the Midlatitudes

AbstractThis study uses a unique combination of geostationary and low‐Earth orbiting satellite‐based lightning and precipitation observations, respectively, to examine the evolution of deep convection during the tropical cyclone (TC) lifecycle. The study spans the 2018–2021 Atlantic Basin hurricane seasons and is unique as it provides the first known analysis of total lightning (intra‐cloud and cloud‐to‐ground) observed in TCs through their extratropical transition and post‐tropical cyclone (PTC) phases. We consider the TC lifecycle stage, geographic location (e.g., land, coast, and ocean), shear strength, and quadrant relative to the storm motion and environmental shear vectors. Total lightning maxima are found in the forward right quadrant relative to storm motion and downshear of the TC center, consistent with previous studies using mainly cloud‐to‐ground lightning. Increasing environmental shear focuses the lightning maxima to the downshear right quadrant with respect to the shear vector in tropical storm phases. Vertical profiles of radar reflectivity from the Global Precipitation Measurement mission show that super‐electrically active convective precipitation features (>75 flashes) within the PTC phase of TCs have deeper mixed phase depths and higher reflectivity at −10°C than other phases, indicating the presence of more intense convection. Differences in the net convective behavior observed throughout TC evolution manifest in both the TC‐scale frequency of lightning‐producing cells and the intensity variations amongst individual convective cells. The combination of continuous lightning observations and precipitation snapshots improves our understanding of convective‐scale processes in TCs, especially in PTC phases, as they traverse the tropics and mid‐latitudes.

Achieving high strength and high-electrical-conductivity of Cu-Ni-Si alloys via regulating nanoprecipitation behavior through simplified process

Overcoming the tradeoff between mechanical strength and electrical conductivity is a long-standing challenge in developing advanced copper alloys for industrial applications. Herein, we report a new strategy to obtain high strength and good conductivity of Cu-Ni-Si-Ca alloy by introducing and regulating the discontinuous precipitation (DP) and continuous precipitation (CP) behaviors. The DP process combined with thermomechanical treatment was exploited to expedite the precipitation kinetics, whilst the competition between DP and CP was utilized to inhibit the nucleation and growth of continuous precipitation phase (CPP). The resultant copper alloy exhibits superior comprehensive properties with a yield strength of 956 MPa, fracture strength of 989 MPa, and electrical conductivity of 34.1 % IACS. The improved electrical conductivity is attributed to the heterogeneous-nucleation dominant DP, while the high strength stems from the combination of strain hardening and precipitation strengthening of δ-Ni2Si and t-Ni3Si precipitates. Notably, the precipitation strengthening arises from both the dislocation passing and cutting mechanisms, with the strongly ordered DO22-type (t-Ni3Si) phase contributing approximately 202 MPa to the overall strength through the cutting mechanism. This work offers a new pathway for alloy design of high-strength and high-electrical-conductivity copper alloys, by regulating coherent ordered nanoprecipitates through DP and CP.

Characterizing Short-Time Aging Precipitation Behavior of a Novel Nickel-Iron-Based Alloy via Electrical Performance.

In this paper, the precipitation behavior and its effect on resistivity in a new type of nickel-iron-based alloy during short-term aging were investigated. During the aging process, the γ' phase increases in average size and decreases in number, with its area fraction fluctuating over time. This fluctuation is caused by the mismatch in the redissolution and growth rates of the γ' phase. As the area fraction of the γ' phase increases, the content of solute atoms in the matrix that scatter electrons decreases, lowering the resistivity of the alloy. Additionally, the continuous precipitation of M23C6 at grain boundaries during aging causes the resistivity to gradually increase. This paper explains the fluctuation in the total amount of γ' phase during short-term aging and proposes a new method for characterizing the precipitation behavior of the γ' phase in the novel alloy using the relative trend of resistivity changes.

Hydroxide-Source-Dependent Polymorphism and Phase Stability of Cobalt(II) Hydroxides in Diffusion-Driven Systems.

Hydroxides of cobalt(II) exist predominantly in two polymorphic forms, namely, the blue-green α-form [α-Co(OH)2] and reddish β-form [β-Co(OH)2]. These hydroxides have a layered structure with interlayer galleries of around 7 and 4 Å, respectively, for α- and β-Co(OH)2. In most of the previous studies, both the polymorphs were synthesized separately, and a few of them showed that the α-form gets converted to a thermodynamically more stable β-form via physical processes. In the present work, we have optimized the conditions for the simultaneous synthesis of both polymorphs under identical conditions in the same reactor using the 1D reaction-diffusion framework by employing different outer electrolytes. We found that the polymorph chemistry of Co(OH)2 depends on the source and concentration of OH- rather than other reaction conditions or later physical transformation. The products are characterized to confirm their morphology, structure, and chemical environment. We observed that the use of NaOH and NH4OH as the OH- precursor leads to α-Co(OH)2 only; however, with NaOH, a continuous precipitate is formed, and with NH4OH, periodic precipitation is formed. On the other hand, with hydrazine (HYZ) as the OH- source, Liesegang bands of α-Co(OH)2 and β-Co(OH)2 as granules are formed throughout the diffusion reactor. Another intriguing observation on the HYZ system is that at its high concentration, the bands of α-Co(OH)2 get converted to β-Co(OH)2. We articulate the reasons and mechanism of those observations.

High-temperature creep mechanism of Ti-Ta-Nb-Mo-Zr refractory high-entropy alloys prepared by laser powder bed fusion technology

Creep resistance, which is one of the most important deformation modes, is rarely reported for refractory high entropy alloys (RHEAs). The experiment investigated the high-temperature creep mechanism of Ti-Ta-Nb-Mo-Zr RHEA prepared by laser powder bed fusion (LPBF) technology. The high cooling rate of LPBF suppresses most of the elemental segregation, but there are still over-solidified precipitates and a few continuous precipitates (CP). In the range of 923–1023 K, the stress exponent and activation energy were determined to be 3.2–3.4 and 261.5 ± 19.5 kJ/mol, respectively. Compared with other conventional alloys and HEAs, a large reduction of the minimum creep rate is found in the LPBF-built Ti1.5Ta0.5NbZrMo0.5 RHEA, indicating a significant improvement in high-temperature properties. The dislocation tangles at the interface is formed during the creep process and new Zr-rich CP phases are generated in the dislocation tangles region. The interfacial dislocation tangles is the result of the interaction between dislocations and two-phase mismatch stresses. The dislocation tangles prevents dislocations from further cutting the matrix phase, which is very favorable to the high-temperature creep performance. At the same time, the formation of this dislocation tangles greatly accelerates the nucleation process and growth rate of the new CP phase. The present work provides a pathway to design novel HEAs with improved high-temperature creep resistance.

Variation of nitrate sources affected by precipitation with different intensities in groundwater in the piedmont plain area of alluvial-pluvial fan

A substantial reservoir of nitrogen (N) in soil poses a threat to the quality and safety of shallow groundwater, especially under extreme precipitation that hastens nitrogen leaching into groundwater. However, the specific impact of varying precipitation intensities on the concentration and sources of nitrate (NO3−) in groundwater across diverse hydrogeological zones and land uses remains unclear. This study aims to elucidate the fluctuations in NO3− concentration, sources, and controlling factors in shallow groundwater under different intensities of precipitation (extreme heavy precipitation and continuous heavy precipitation) in a typical alluvial-pluvial fan of the North China Plain by using stable isotopes (δ2H–H2O, δ18O–H2O, δ15N–NO3-, δ18O–NO3-), hydrochemical analyses and the SIAR model. Affected by extreme heavy precipitation the depleted isotopes of δ2H–H2O and δ18O–H2O in groundwater of the entire area suggested the rapid recharge of fast flow by precipitation. The enriched isotopes of δ2H–H2O and δ18O–H2O of north part in alluvial fan after continuous heavy precipitation showed the recharge of translatory flow of soil water. NO3−concentrations increased to 78.9 mg/L after extreme heavy precipitation and increased to 105.3 mg/L after continuous heavy precipitation when compared to those in normal year (56.8 mg/L) of north part of the alluvial fan. However, NO3− concentrations had slight variation after continuous heavy precipitation of south part of the fan due to the deep vadose zone. The contribution ratio of sources of NO3− in groundwater by using SIAR analysis revealed manure & sewage (MS) as the primary NO3− source (accounting for 59.7–78.1%) before extreme heavy precipitation, chemical fertilizer (CF) making a minor contribution (6.9–17.3%). Different precipitation events and land use types lead to changes in NO3− sources. Affected by extreme heavy precipitation, the contribution of MS decreased while CF increased, particularly in vegetables (26.2–28.1%) and farmland (29.2–34.7%). After continuous heavy precipitation, MS increased again, particularly in vegetables (50.0%) and farmlands (20.4–66.4%), with CF either increasing or remaining steady. This indicated that continuous heavy precipitation accelerated the leaching of nitrogen (organic manure application) stored in deep soil to groundwater and it has a larger influence on the increasing of NO3− concentrations of groundwater than extreme heavy precipitation which carried nitrogen (chemical fertilizer application) in shallow soil to groundwater by fast flow. These findings underscore the importance of considering soil chemical N stores and their implications for groundwater contamination mitigation under future extreme climate scenarios, particularly in agricultural management practices.

First Report of Plumed Cockscomb (Celosia argentea var. plumosa) Stem Blight Caused by Phytophthora nicotianae in Taiwan.

Celosia spp. is a widely cultivated ornamental plant in gardens or parks in Taiwan. In September 2021, withering leaves and grayish-brown lesions were observed on the lower stem of plumed cockscombs (C. argentea var. plumosa) in Taichung City, with an incidence of about 22% in 136 plants after continuous precipitation, impacting the aesthetic value of the landscape. Symptomatic plants were collected, surface disinfected with 70% EtOH for ~20 sec., blotted dried, and excised diseased tissues (~ 3×3 mm2) were placed on 2% water agar. Four representative isolates were obtained after purification and the colonies were white with aerial and non-septated hyphae on V8 agar for 7 days. Sporangia were ovoid, ellipsoid or obpyriform, papillate, (26.3-55.9) 38.0 × 29.0 (20.1-40.6) µm (n = 200) (Ahonsi et al. 2007). Chlamydospores were spherical, terminal or intercalary, 26.0 (15.1-40.4) µm (n = 200). All isolates belong to A2 mating type with amphigynous antheridia and plerotic oospores, 21.0 (17.7-25.7) µm (n = 200), resembling the descriptions of Phytophthora (Erwin & Ribeiro 1996). For molecular identification, sequences of the ITS, β-tubulin (β-tub), and EF-1α regions of all isolates were amplified using ITS1/ITS4, TUBUF2/TUBUR1, and ELONGF1/ELONGR1 primers, respectively (White et al. 1990; Kroon et al. 2004). BLAST analyses of isolates cap1-2 (ITS: OQ581785; β-tub: OQ590022; EF-1α: OQ590026), cap1-3 (ITS: OQ581786; β-tub: OQ590023; EF-1α: OQ590027), cap2-1 (ITS: OQ581787; β-tub: OQ590024; EF-1α: OQ590028), and cap2-2 (ITS: OQ581788; β-tub: OQ590025; EF-1α: OQ590029) showed 100% of ITS identity, 99.5 to 99.9% of β-tub identity, and 99.4 to 99.6% of EF-1α identity with Phytophthora nicotianae (ITS: MG865551; β-tub: MH493987; EF-1α: MH359043). Phylogenetic trees were constructed using concatenated ITS, β-tub, and EF-1α sequences based on maximum likelihood with a GTR+G model in MEGA X and Bayesian inference method in Geneious Prime 2022.2. All isolates were clustered in P. nicotianae with similar topology, thereby were identified as P. nicotianae. To confirm pathogenicity, 7 to 10-day-old seedlings and 6-week-old plumed cockscomb plants were inoculated in separate trials and each experiment was conducted twice. For each seedling, the lower stem was inoculated with 50 μl of zoospore suspension (104 zoospores/ml), 3 plants per isolate, and then incubated at 30±2℃ with 12 h light. For adult plants, each was inoculated with mycelial plugs from one V8 plate of 10-day-old P. nicotianae, 5 plants per isolate, and incubated at 25±2℃ in a greenhouse. Control plants were inoculated with sterile water and V8 agar plugs, respectively. Stem and root rot were observed on seedlings 4 days after inoculation while wilting and lower stem browning were observed on adult plants 2 months after inoculation. All control plants remained healthy at the end of repeated trials and identical pathogens were re-isolated only from symptomatic plants, thus fulfilling Koch's rules. P. nicotianae has been reported causing root rot and stem necrosis not only on cockscomb (C. plumosa Hort. ex Burvenich) in Argentina (Frezzi 1950), but also infecting several ornamental plants recently in Taiwan (Ann et al. 2018). To our knowledge, this is the first report of stem blight caused by P. nicotianae on plumed cockscombs in Taiwan. This finding suggests limited options for landscaping and the host preference of the isolates obtained in this study should warrant further studies.

Microgels with controlled network topologies by photocrosslinking-assisted continuous precipitation polymerization

In this study, we present a new synthesis methodology based on photo-crosslinking-assisted continuous precipitation polymerization which allows controlling the distribution of crosslinks in microgels. In our approach we substituted conventional crosslinking agent by a comonomer carrying photo-crosslinkable 4-oxocyclopent-2-en-1-yl group. Microgel size, morphology, distribution of crosslinks and packing density of the polymer chains are studied as a function of retention time (Rt) in the flow reactor. Dynamic and static light scattering (DLS and SLS) as well as small angle X-ray scattering (SAXS) proved an excellent level of control over the distribution of crosslinks in microgels during the polymerization process. These results were confirmed by atomic force microscopy (AFM), indicating a difference in microgel stiffness and arrangement of the polymer network as resulting from increased Rt.

Influence of Aging Condition on the Characteristics of Continuous Precipitates of AZ80 Magnesium Alloy

The aim of this work is to evaluate the characteristics of continuous precipitates (CP) developed within the grain and grain boundary precipitates through statistical analysis of the number density and size (i.e., length and width) at varying aging conditions of AZ80 Mg alloy. Scanning electron microscopy illustrates the characteristics and features of precipitates, distinctively. The results reveal an increment of number density, whereas the reduction in the size of precipitates with decrease in the aging temperature for the varying aging times. The variation in hardness values at different aging conditions has been ascribed to this.

Cobalt enrichment and metallogenic mechanism of the Galinge skarn iron deposit in the Eastern Kunlun metallogenic belt, western China

Skarn iron deposits, as representative examples of Co-rich magmatic-hydrothermal deposits, are attracting increasing attention due to rising cobalt demand worldwide. However, the specific Co enrichment mechanisms and metallogenic processes in skarn deposits remain elusive. This study presents high-precision in situ U–Pb geochronological data for garnet from skarns, major and trace element analyses of sulfarsenides and sulfides, and X-ray mapping in the Galinge deposit. The Galinge skarn iron deposit formed at 237.1 ± 0.3 Ma (garnet U–Pb dating), during which time the region was in the post-collisional stage. During this period, the crust was thickened, causing delamination of the lithospheric mantle, which further led to the upwelling of asthenospheric materials and partial melting of the lower crust. As the resultant mixed magma ascended, it reacted with carbonate strata to form skarn deposits. Cobalt shows two occurrence modes in the Galinge deposit: independent cobalt minerals such as skutterudite and cobaltite, and isomorphic substitution of Co with other metals in ore minerals (arsenopyrite, pyrrhotite, sphalerite, pyrite, magnetite, and chalcopyrite). Our results revealed that arsenopyrite is the most cobalt-enriched ore mineral in the Galinge deposit, with an average Co content of 34,077 ppm. Other minerals generally contain insignificant Co contents of less than 500 ppm, including sphalerite (471 ppm) > pyrite (194 ppm) > pyrrhotite (145 ppm) > alabandite (∼100 ppm) > magnetite (7 ppm) > chalcopyrite (2 ppm). In arsenopyrite, cobalt and nickel replace iron in accordance with the inverse correlation between the concentrations of cobalt and nickel (wt%) and that of iron. In pyrite and chalcopyrite, a portion of the isomorphic cobalt substitutes for Fe or Cu. The weak correlation between Co (ppm) and Cu or Fe (wt%) indicates that only isomorphic cobalt is carried out by substituting Fe or Cu. The negative correlation between Co + Fe and Zn or Mn suggests that cobalt and iron replace Zn or Mn in sphalerite and alabandite. No evidence of element substitution was observed in pyrrhotite. Our study highlights that during the early mineralization stage, cobalt in the magmatic-hydrothermal fluids migrated in the form of CoCl42-. Subsequently, under the influence of an increase in pH, CoCl42- reacts with H3AsO30 to form CoAs3 (skutterudite). With the continuous precipitation of arsenides and sulfarsenides, the As/S (reduced) ratio decreased, leading to the CoAs3 (skutterudite) changing to CoAsS (cobaltite).

The permeability evolution mechanism of ore-bearing strata during acid in-situ leaching of uranium: A case study of Bayanwula uranium mine in Inner Mongolia of China

Uranium mainly comes from ISL of sandstone-type uranium deposits in China. The change of porosity and permeability caused by blockage of ore-bearing strata is one of the most serious problems in acid ISL of uranium. In this paper, the groundwater tracer test was carried out before and 1 year after ISL to explore the pore and permeability evolution characteristics of the ore-bearing layer during ISL. The test results showed that the leaching solution migrated along two seepage channels and the water-bearing medium was isotropic. After 1 year of ISL, the flow rate of the leaching solution decreased obviously. However, the flow rate of the leaching solution in slower channel decreased more than that in the faster channel in all directions, which was caused by the more adequate chemical reactions between the leaching solution and the minerals of the ore-bearing layer and the more corresponding precipitation in the slower channel. In addition, the flow rate along the direction of groundwater flow decreased less than that in the direction of vertical groundwater flow. This was closely related to the transformation of aquifer medium by hydrodynamic field. Initial stage of ISL, the occurrence of plugging is closely related to the precipitation-dissolution process of iron and aluminum minerals under the change of pH, which is accompanied by the continuous precipitation of gypsum.

Enhanced strength of L12-strengthened (FeCoNi)79.5Cr10.5Al5Ti5 high-entropy alloy via Ta alloying and its refined strengthening mechanism model

In this study, we enhance the strength of L12-strengthened high-entropy alloy, proposed in our previous study, by Ta alloying. Continuous precipitation is promoted, resulting in a remarkably high yield strength of 1144.8 ± 19.3 MPa. Furthermore, we suggest a refined strengthening mechanism model, based on the superposition of multiple mechanisms.