Electromigration Research Articles

Salt-Concentrated Electrolyte Constructing High Elasticity Modulus Interphase for Li-Rich Layered Oxide Cathode.

Stable electrolytes are urgently required for lithium-ion batteries based on lithium-rich layered oxides (LLOs), which generally suffer from fast capacity and voltage decay at high voltages up to 4.8 V. Herein, we report a salt-concentrated electrolyte consisting of 4 M lithium hexafluorophosphate (LiPF6) salt in ester solvents of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) to alleviate the above challenges. The solvent structure in the 4 M electrolyte shows more volatile DMC integrated with Li+ and more free antioxidative FEC compared with a 1 M electrolyte, broadening the operation voltage. Simultaneously, this electrolyte endows a thin yet high elasticity modulus LiF-rich interphase on the LLOs surface, which can effectively prevent diverse side reactions and transition metal migration, consequently improving the electrochemical performance with a voltage decay of only 0.46 mV/cycle and capacity retention of 80.3% after 500 cycles. This simple and effective approach boosts the development of high-energy-density batteries using LLOs.

Porphyrin protonation induces decoupling of trace metals in petroleum

The mechanism of migration of trace metals in petroleum systems is poorly understood, which limits our understanding of organic–inorganic interactions and their application in tracing oil sources. Based on a molecular model of metalloporphyrin, numerical simulations involving density functional theory have revealed that porphyrin protonation is associated with trace-metal decoupling in petroleum. Trace metals readily form covalent bonds with weakly protonated porphyrin N to form stable compounds. However, the metals may be decoupled at lower fluid pH owing to increased N protonation, which activates the formation of ionic bonds with O2−. The released metals may then be fixed in authigenic calcite cement (ACC) reservoirs through substitution of Ca. For Mg, Mn, and Fe, the decoupling order is Mg > Fe > Mn, whereas that for the substitution of Ca is Mn > Fe > Mg, reflecting the complexity of organic–inorganic interactions and indicating the potential application of metals in fingerprinting oil sources. This case study of the southern Junggar Basin, China, revealed that Mn, Fe, and Mg enrichment of ACC may provide indications of Paleozoic, Mesozoic, and Cenozoic petroleum systems, respectively, providing a potential new approach for the tracing of oil sources in petroleum basins.

Modulating Local Oxygen Coordination to Achieve Highly Reversible Anionic Redox and Negligible Voltage Decay in O2‐Type Layered Cathodes for Li‐Ion Batteries

AbstractO2‐type layered oxides have emerged as promising cathode materials for high‐energy lithium‐ion batteries, offering a solution to mitigate voltage decay through reversible transition metal (TM) migration between TM and Li layers during cycling. However, achieving a fully reversible oxygen redox remains a significant challenge. Here, this is addressed by introducing Li─O─Li configurations in the layered structure of Li0.85□0.15[Li0.08□0.04Ni0.22Mn0.66]O2 (O2‐LLNMO), where □ represents vacancies. This adjustment alters the redox‐active oxygen environment and increases the energy gap between the O 2p nonbonding and TM─O antibonding bands. As a result, the contribution of lattice oxygen to capacity is significantly enhanced, improving the reversibility of oxygen redox processes. The O2‐LLNMO cathode demonstrates minimal voltage decay (0.13 mV per cycle) and excellent cycling stability, retaining 95.8% of its capacity after 100 cycles. A novel strategy is presented to design high‐performance layered oxides with stable anionic redox activity, advancing the development of next‐generation lithium‐ion batteries.

Effect of background ions and physicochemical factors on the cotransport of microplastics with Cu2+ in saturated porous media

Microplastics (MPs) in subsurface environments are migratory and can carry heavy metals, increasing the extent of MP and heavy metal pollution. This study used quartz sand-filled column experiments to investigate the adsorption and cotransport behaviours of PS-MPs, O3, UV-aged PS-MPs, and Cu2+ at different MP concentrations, ionic strengths, and ionic valences in a saturated porous medium. The results showed that when MPs migrate alone in the absence of an ionic background, higher concentrations have increased mobility. In contrast, an increase in the background ion concentration or ion valence inhibits the individual transport capacity of PS-MPs. An increase in the concentration of background ions or elevation in the valence state promotes Cu2+ transport because of the action of the double electric layer on the surface of the colloid and the electrostatic repulsive forces combined with the background ions. The adsorption capacity of aged PS-MPs was stronger than that of PS-MPs because of the binding of the aged PS-MPs to Cu2+ through complexation and electrostatic attraction. In the binary system of PS-MPs/Cu2+, PS-MPs promoted Cu2+ transport and the mobility of Cu2+ loaded by PS-MPs decreased with increasing background ion concentration. The cotransport results showed that MPs promote Cu2+ transport in the following order: O3-aged Ps > UV-aged Ps > Ps, as the increasing cation concentration in the MPs and Cu2+ occupies the PS surface adsorption sites. Overall, PS is an effective carrier for Cu2+. These findings offer fresh exploration concepts for the joint migration of MPs and heavy metals in underground settings.

Migration and Transformation of Heavy Metals During the CO2-Assistant Thermal Treatment of Oily Sludge

Thermal treatment has significant advantages in resource recovery for oily sludge (OS). However, the instability of heavy metals (HMs) within the residue poses a considerable risk of secondary pollution. This study explored the migration and transformation of HMs from OS under varying conditions (i.e., temperature, constant-temperature duration time, and different ratios of O2 and CO2). The elevation of the pyrolysis temperature augmented the decomposition of organic matter and total petroleum hydrocarbons (TPHs). However, the increased temperature also diminished the stabilization of HMs, and facilitating the HM’s transfer to oil and gas, particularly for HMs (i.e., As and Pb) with low boiling points. The constant-temperature duration time exhibited a weak impact on HM transformation, but the internal heating mechanism of microwave pyrolysis promoted the stabilization of HMs through vitrification. The existing O2 with oxidizing properties facilitated the oxidation of organic matter and TPHs to CO2 and H2O, which also promoted the transformation of HMs into oxidized states for stabilization. Comparatively, CO2 promoted the thermal cracking and disrupted the stability of HMs to a certain extent. Above all, this work revealed the migration and transformation of HMs in OS varied with the thermochemical methods and possessed an important significance for the immobilization and stabilization of HMs.

Comparison of the Ability of Woody Plants of Different Species to Accumulate Heavy Metals in Urban Environment

Soil and aerotechnogenic migration of metals into woody plants (birch (Betula pendula) and balsam poplar (Populus balsamifera)) from technogenic zones of Tyumen was studied. Soil and tree leaves were sampled in the conditionally background area, near the airport, railway station and bus station, as well as in the area of enterprises: engine-building, oil refinery, battery and metallurgical plants. The content of acidsoluble form of metals in soils and leaves was determined by atomic emission spectroscopy. It was revealed that the accumulation of metals in soils from the anthropogenic zones of Tyumen compared to the control decreased in the series Pb>Cd>Cr>Cr>Ni>Zn>Cu>Fe>Co>Mn and reached 20 times. The accumulation of metals by birch leaves was found to decrease in the series Pb>Cr>Fe>Co>Cu>Cu>Ni>Zn>Mn>Cd, and by poplar leaves – Cr>Fe>Pb>Zn>Cd>Cu>Co>Mn>Ni. The accumulation and migration of metals in soils and trees from the urban environment were analyzed, which allowed us to identify Cd, Pb and Cr as metals with the “highest ecological risk”.

Formation mechanism of Fe oxyhydroxides and behavior of metals during the oxidation of submarine sulfides at the Wocan-1 hydrothermal field, Carlsberg Ridge

Hydrothermal sulfides undergo complex oxidation process under seawater conditions, which has the potential to impact resource values and marine environments. However, the oxidation process is not fully explored, particularly regarding the transformation of minerals and the behavior of metals. In this paper, we conducted detailed mineralogical and geochemical analyses on a series of samples with varying degrees of oxidation, collected from the Wocan-1 hydrothermal field, Carlsberg Ridge, Northwest Indian Ocean. The principal purpose is to illuminate the formation and transformation of Fe (oxyhydr)oxides, and further to reveal the migration and redistribution of key metals throughout the oxidation process. We identified four types of Fe(−Si) (oxyhydr)oxides with two distinct formation mechanisms. Three Fe (oxyhydr)oxides are the direct oxidation products of pyrite and marcasite, while Fe-Si (oxyhydr)oxide precipitates from low-temperature hydrothermal fluids. Thin Fe (oxyhydr)oxide forms as the secondary product of euhedral pyrite at the early stage of oxidation. Pseudomorphic Fe (oxyhydr)oxide with low Fe contents, occurs as the replacement of euhedral marcasite. Filamentous Fe (oxyhydr)oxide, enriched in trace metals, is attributed to the uniform oxidation of subhedral pyrite-marcasite intergrowth. Moreover, major and trace elements occur multiple migrations and redistributions among primary sulfides, secondary products, and seawater. Notably, Fe (oxyhydr)oxides, through the sequestration mechanism, not only retain Cu and Zn released by the oxidation of primary sulfide minerals, but also scavenge Cu from seawater. However, the dissolution of Pb, As, Mo, and Co exceeds the amount retained during the oxidation, indicating that the potential release of toxic metals into the environment could pose a threat to the local ecosystem. These new insights can provide an initial foundation for the effect of submarine oxidation on economic values of sulfides and ecological environments of deep sea.

New insights into sustainable in-situ fixation of heavy metals in disturbed seafloor sediments

To address the issues of plume formation and heavy metal ion release during deep-sea mining operations, this study employed multi-sourced mineral composite roasting materials (MMCCM) of varying sizes. An in-situ capping technique was applied within a simulated system to immobilize heavy metals in contaminated sediments. The results demonstrated that capping with MMCCM of different sizes significantly suppressed the upward migration of Cu, Co, and Ni from sediments into the overlying seawater following disturbance. Ion diffusion was identified as a key mechanism driving heavy metal migration. By calculating the release rates of heavy metals during both the disturbed and undisturbed phases, it was found that the application of MMCCM induced a negative diffusion of heavy metals, indicating that the MMCCM-sediment layer functioned as a "sink" for heavy metals. FTIR and XPS analysis showed that the primary mechanisms for heavy metal removal by MMCCM were electrostatic attraction and complexation-precipitation. Additionally, capping with MMCCM facilitated the transition of heavy metals from labile to stable forms within the sediments. Through comprehensive evaluation, the long-term effectiveness of the fixed effects was demonstrated as follows: large MMCCM (L@MCM) > medium MMCCM (M@MCM) > small MMCCM (S@MCM) > powder MMCCM (P@MCM). Finally, we proposed future research directions and introduced the DQSE framework for the sustainable application of MMCCM. Based on the above findings, this study provides new insights and research references for the in-situ immobilization of heavy metals and plume reduction during future deep-sea mining processes.

Role of mechanical stress localizations on the radiation hardness of AlGaN/GaN high electron mobility transistors

Abstract Multi-material, multi-layered systems such as AlGaN/GaN high electron mobility transistor (HEMTs) contain residual mechanical stresses that arise from sharp contrasts in device geometry and materials parameters. These stresses, which can be either tensile or compressive, are difficult to detect and eliminate because of their highly localized nature. We propose that their high stored internal energy make potential sites for defect nucleation sites under radiation, particularly if their locations coincide with the electrically sensitive regions of a transistor. In this study, we validate this hypothesis with molecular dynamic simulation and experiments exposing both pristine and annealed HEMTS to 2.8 MeV Au+3 irradiation. Our unique annealing process uses mechanical momentum of electrons, also known as the electron wind force (EWF) to mitigate the residual stress at room temperature. High-resolution transmission electron microscopy (TEM) and cathodoluminescence spectra reveal the reduction of point defects and dislocations near the two-dimensional electron gas region of EWF-treated devices compared to pristine devices. The EWF-treated HEMTs showed relatively higher resilience with approximately 10% less degradation of drain saturation current and ON-resistance and 5% less degradation of peak transconductance. Both mobility and carrier concentration of the EWF-treated devices were less impacted compared to the pristine devices. Our results suggest that the lower density of nanoscale stress localization contributed to the improved radiation tolerance of the EWF-treated devices. Intriguingly, the EWF is found to modulate the defect distribution by moving the defects to electrically less sensitive regions in the form of dislocation networks, which act as sinks for the radiation induced defects and this assisted faster dynamic annealing.

Comparative Study of High Voltage Spinel∥Lithium Titanate Lithium‐ion Batteries in Ethylene Carbonate Free Electrolytes

AbstractA persistent obstacle towards the realization of high voltage cathodes is electrolyte instability where oxidation and transition metal dissolution manifest in rapid capacity failure with both issues connected to the presence of ethylene carbonate in the electrolyte. Here, alternative electrolyte co‐solvents are investigated and compared, where the cyclic carbonate is replaced with sulfones ethyl methyl sulfone (EMS) and tetra methylene sulfone (TMS) and fluoroethylene carbonate (FEC). The best full cell performance was observed for cells cycled in a FEC/EMC (3/7) and FEC/EMC (1/1) electrolytes which exhibited 84–85 % capacity retention after 500 cycles. TMS/EMC (3/7), was determined to be the best performing sulfone electrolyte and maintained 71 % capacity after 500 cycles. Post‐mortem XPS analysis indicated different film forming mechanisms for the respective co‐solvent. A thicker cathode electrolyte interphase (CEI) on the LNMO was observed for the FEC containing electrolytes (relative to when TMS was used as the co‐solvent) indicating more effective passivation of the reactive cathode surface which correlated well with the enhanced cycling stability observed. For LTO, more evidence of transition metal migration and a thicker solid electrolyte interphase (SEI) layer was observed for the sulfone electrolyte suggesting more parasitic anode‐electrolyte interactions and an inability to mitigate Mn2+/Ni2+ crosstalk.

Asymmetric Palladium Migration for Synthesis of Chiral-at-Cage o-Carboranes.

Metal migration strategy can offer BH functionalization of o-carboranes at different positions from where initial bond activation occurs to achieve bifunctionalized o-carboranes in one reaction. We report in this article an enantioselective 3,4-bifunctionalization of o-carboranes via asymmetric Pd migration with a high efficiency and up to 98% ee. This asymmetric catalysis has a broad substrates scope, leading to the preparation of a class of chiral-at-cage o-carborane derivatives. The enantiocontrol model is suggested on the basis of density functional theory (DFT) results, where the chiral Trost ligand plays a crucial role in this enantioselective Pd migration from exo-alkenyl sp2 C to the cage B(4) position of o-carborane.

Triggering Reversible Intercalation-Conversion Combined Chemistry for High-Energy-Density Lithium Battery Cathodes.

Combining intercalation and conversion reactions maximizes the utilization of redox-active elements in electrodes, providing a means for overcoming the current capacity ceiling. However, integrating both mechanisms within a single electrode material presents significant challenges owing to their contrasting structural requirements. Intercalation requires a well-defined host structure for efficient lithium-ion diffusion, whereas conversion reactions entail structural reorganization, which can undermine intercalation capabilities. Based on the previous study that successfully demonstrated reversible intercalation-conversion chemistry in amorphous LiFeSO4F, this study aims to provide an in-depth understanding on how this can be enabled. Experimental and theoretical investigations of a model system based on tavorite-structured LiFeSO4F revealed that amorphization governs the activation and reversibility of the combined reactions. Enhanced reversibility is achieved through the facile migration of transition metals within the amorphous matrix. Unexpectedly, it is found that amorphization also narrowed the voltage gap between the intercalation and conversion reactions. This voltage-gap reduction is explained by the thermodynamic metastability of the amorphous phase. The applicability of the approach to other intercalation hosts is further demonstrated, showing that amorphization enables reversible intercalation and conversion. These findings suggest a new strategy that leverages the full potential of intercalation and conversion reactions, introducing new avenues for cathode design.

Unveiling heavy metal(loid) contamination and migration at an abandoned smelting site: Integrated geophysical and hydrological analyse

The heavy metal contamination at abandoned smelting sites is receiving increasing attention. This study focuses on an abandoned lead–zinc smelting site and uses several methods (such as soil sampling, geophysical exploration, and groundwater monitoring) to systematically investigate the contamination characteristics, distribution patterns, and migration mechanisms of heavy metal(loid) in soil and groundwater. A geological structure model of the study area was established through drilling data and geophysical techniques (Ground penetrating radar (GPR) and Electrical resistivity tomography (ERT)), revealing the relationships among soil resistivity, electromagnetic wave reflection characteristics, and geological structure. This study revealed that heavy metal contamination in soil was concentrated mainly northwest of the site and was closely related to historical smelting activities. The presence of heavy metal(loid)s in groundwater had a complex correlation with soil physicochemical properties and environmental elements, and its distribution was influenced by both hydrogeological conditions and soil properties. This study also investigated the effects of the soil water content (SWC) and soil hydraulic conductivity (Ks) on heavy metal(loid)s migration and reported that high SWC and Ks contribute to the dissolution and migration of heavy metals. In addition, a 3D visualization model of heavy metal contamination plumes was established via Voxler software. This model intuitively demonstrated the migration and diffusion of heavy metal(loid)s in the underground environment, offering a novel perspective on their subsurface behavior. The research results provide important information for understanding the migration of heavy metal(loid)s in soil-groundwater systems.

Effect of Electrode Positioning on Electrokinetic Remediation of Contaminated Soft Clay with Surface Electrolyte.

Soft clay contamination is an increasingly global issue with significant implications for land development and human health. Electrokinetic remediation (EKR) has demonstrated significant potential for cleaning contaminated soils. It is crucial to develop efficient processes that minimize environmental impact and reduce costs. A series of citric acid (CA)-enhanced EKR tests were conducted using a novel experimental setup, with the electrolyte positioned above the soil surface, to examine the impact of four different electrode arrangements on the effectiveness of EKR. The position of the electrode end had a significant impact on the migration of ions in the anolyte and catholyte, which in turn affected the volume reduction in the anolyte, the magnitude of the current, and the migration of heavy metals. The electrode arrangement mode c (electrodes suspended in the electrolytes) can enhance the migration of the anolyte and reduce the drainage of the soil, making it an effective measure for improving the removal rate of heavy metals. After the heavy metal remediation is complete, the bearing capacity of the soil should be increased. Changing the electrode arrangement to mode d (anode suspended in the anolyte, a very small part of the cathode inserted into the soil) is an effective measure for reducing the soil water content and improving soil strength.

Study on the source identification and migration and transformation characteristics of heavy metal pollution in sediments of Chaohu Lake Tongyang River Basin.

Heavy metal pollution in soil and groundwater is difficult to detect in time because of its long-term accumulation. This poses a severe hazard to the ecosystem security in polluted areas. Considering the Tongyang River Basin of the Chaohu Lake water system as the research object, various pollution evaluation methods, Geographic Information System (GIS) source analysis models, adsorption and desorption experiments, and mathematical models were used. Based on the data of the heavy metal content in the soil and river sediments in the study area, regional heavy metal pollution evaluation, spatial distribution characteristics, source identification, and lake loss analysis were conducted to evaluate the current situation of environmental pollution, pollution sources, and migration and transformation of heavy metals in the basin. The results show that the heavy metals in the soil of the basin are mainly distributed from the southwest to the northeast and the island distribution to the east of Tongyang Town. The Cd, Cu, Zn, and Pb concentrations are higher in the sediment than in the soil. The Unmix analytical model was established. The natural source of heavy metals in the Tongyang River Basin and the composite pollution source of traffic-production and life showed a high correlation. According to the one-dimensional steady-state model, the concentrations of the heavy metals are in the following descending order: Zn, Cr, Pb, Cu, Ni, and Cd. The amounts of these elements entering the lake annually are 1993.04, 1028.1, 372.47, 301.72, 308.80, and 19.46 kg, respectively (a total of 4023.6 kg).

Electromigration in Cu–Cu joints: Measurement of activation energy and polarity effect

Electromigration (EM) has been a pivotal reliability challenge for interconnects, but there are only few studies on EM in Cu–Cu joints. In this work, accelerated EM tests for the Cu–Cu joints were conducted at three temperatures (150 °C, 179 °C, and 208 °C) and the temperature-dependent failures were discussed. The polarity effect of the grain growth behaviors at the bonding interfaces was observed at the opposite electron flows, which may be attributed to the difference in EM-build-up stress conditions and the divergence in atomic fluxes. Moreover, the activation energy (Ea) extrapolated from the three EM temperatures was derived as 0.9 eV. As compared to the solder joints with same dimensions, the Cu–Cu joints possess more than ten times of time-to-failures (TTFs) under the same EM condition.

Impact of ceramic packaging on the quality and safety of Armenian fermented dairy product Matsoun

Background: Packaging is essential for food safety, as it acts as a barrier against contaminants that can cause spoilage and affect human health. The Armenian fermented dairy product, matsoun, is packaged not only in plastic and glass but also in clay pots. However, the impact of traditional packaging on the quality and safety of matsoun, especially heavy metal migration, remains under-researched. Objective: This study aimed to investigate the impact of ceramic packaging material on the quality and safety of matsoun during storage. Specifically, it compared the physicochemical properties (pH, titratable acidity), lactic acid bacteria (LAB) populations, and metal migration during storage. Methods: Six samples of matsoun were prepared and packaged in sterilized glass and ceramic containers. The samples were stored at 4 °C and analyzed on days 1, 7, and 15 of storage. The parameters measured included pH, titratable acidity, and LAB counts (coccus and bacillus). Heavy metal migration (Cd, Pb, Hg, As) was analyzed using atomic absorption spectroscopy. Results: The pH of samples packaged in ceramic and glass containers decreased over 15 days of storage, from 4.61 to 4.24 and 4.6 to 4.27, respectively. Titratable acidity increased in both groups, reaching 1.2 % lactic acid. A decrease in bacilli was observed in ceramic-packaged matsoun. The lead concentration remained constant at 0.0045 ppm across all samples. In ceramic containers, cadmium concentration increased from 0.0015 ppm to 0.0029 ppm by day 15. Conclusion: This study observed a decrease in pH, an increase in titratable acidity, and a relatively constant number of lactic acid bacteria indicating ongoing fermentation. The results showed nondetectable concentrations of arsenic (As) and mercury (Hg). The lead (Pb) concentration in all samples remained within the World Health Organization’s (WHO) allowed limit of 0.02 ppm. However, the concentration of cadmium (Cd) concentration in ceramic-packed increased, exceeding the WHO limit of 0.002 ppm. Further research is necessary to identify the sources of cadmium contamination. Keywords: food packaging, ceramic, matsou​​n​, heavy metal migration, food safety

Recycling of flotation residual carbon from coal gasification fine slag through thermal combustion reaction: Insight into the spatial and temporal multi-scale evolution of typical heavy metals

The necessity for a fundamental comprehension of the migration and transformation patterns of heavy metals in the combustion reaction process is paramount to ensure the effective and targeted prevention and control of heavy metal pollution in the context of large-scale energy utilization of waste coal gasification fine slag. This study aims to reveal the fate of typical heavy metals during the combustion reaction of coal gasification fine slag to provide valuable insight for its clean secondary use. In this work, the thermal combustion reactivity of coal gasification fine slag was initially enhanced through froth flotation, and then the spatial and temporal multi-scale evolution of heavy metals in the flotation carbon-rich fraction was investigated by a series of analytical experiments. The results demonstrate a strong correlation between the volatility of typical heavy metals and the combustion reaction process of the flotation carbon-rich fraction. The volatility of V, Ni, Cu, Zn, and Pb is consistently high, of which the volatility of Zn and Pb is consistently above 50%, while the volatility of Cr, Mn, and Ba exhibits greater temperature sensitivity. As the reaction proceeds, the specific surface area of the solid residue expands, and then the smooth and dense mineral particles dissolve into each other to form a cluster structure simultaneously with the collapse of the pore structure, resulting in the volatility of the heavy metals firstly increasing and then decreasing. Furthermore, alkali metals and alkaline earth metal compounds are effective carriers of Cr, Mn, and Ba in the bottom residual. Additionally, the type and number of crystalline minerals in the bottom residual gradually increase as the reaction progresses. This results in the gradual conversion of the heavy metals bound to unstable carbonate minerals and sulphones into more stable chemical forms. The findings provide novel theoretical support and technical guidance for the environmentally sound and efficient utilization of residual carbon in the waste coal gasification fine slag.

The Effect of Bi Addition on the Electromigration Properties of Sn-3.0Ag-0.5Cu Lead-Free Solder

As electronic packaging technology advances towards miniaturization and integration, the issue of electromigration (EM) in lead-free solder joints has become a significant factor affecting solder joint reliability. In this study, a Sn-3.0Ag-0.5Cu (SAC305) alloy was used as the base, and different Bi content alloys, SAC305-xBi (x = 0, 0.5, 0.75, 1.0 wt.%), were prepared for tensile strength, hardness, and wetting tests. Copper wire was used to prepare EM test samples, which were subjected to EM tests at a current density of approximately 0.6 × 104 A/cm2 for varying durations. The interface microstructure of the SAC305-xBi alloys after the EM test was observed using an optical microscope. The results showed that the 0.5 wt.% Bi alloy exhibited the highest ultimate tensile strength and microhardness, improving by 33.3% and 11.8% compared to SAC305, respectively, with similar fracture strain. This alloy also displayed enhanced wettability. EM tests revealed the formation of Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) at both the cathode and anode interfaces of the solder alloy. The addition of Bi inhibited the diffusion rate of Sn in Cu6Sn5, resulting in similar total IMC thickness at the anode interface across different Bi contents under the same test conditions. However, the total IMC thickness at the cathode interface decreased and stabilized with increasing EM time, with the SAC305-0.75Bi alloy demonstrating the best resistance to EM.

Remediation of Pb and Cd contaminated sediments by wheat straw biochar and microbial community analysis

Wheat straw biochar (BC) or modified wheat straw biochar (MBC) could affect the aggregate structure of soil, effectively adsorb heavy metal and reduce the bioavailability of heavy metals in soil. TGA, BET, FTIR and SEM were used to characterize the surface morphology and structure of BC and MBC. The adsorption properties of BC and MBC on Pb(‌II) and Cd(‌II) in solution systems were investigated by batch experiments, and the remediation performance of Pb and Cd contaminated sediment by BC or MBC were studied by pot experiments. The results showed that MBC had a larger specific surface area of 46.04 m2/g and total pore volume 0.0555 cm3/g; the adsorption isotherms of Pb(II) and Cd(II) for BC and MBC were more suitable for Langmuir model (R2 over 0.91), and the maximum adsorption capacities of Pb(II) and Cd(II) by MBC could reach 71.14 and 115.64 mg/g, respectively. BC or MBC promoted the transformation of Pb and Cd from the extractable acid fraction to the oxidizable and residual fraction, reduced the migration of heavy metals and enhanced the stability of aggregates. Therefore, the results provided a perspective for the dredged contaminated sediments used as planting soil. In addition, BC or MBC, as soil amendments, could improve the abundance of microbial community. At the phylum level, the main dominant bacteria were Proteobacteria and Bacteroidetes.