High Al3 Research Articles

A meta-analysis of physicochemical changes in the rhizosphere and bulk soil under woodlands

Monoculture for timber production has been replacing natural environments as the demand for renewable energy sources increases. The lack of nutrient compensation may increase the risk of soil depletion, thus changing soil properties. To summarize the impact of forestry activities in edaphic environments, we present a meta-analysis on the rhizosphere effects of coniferous and broadleaved trees established as monoculture and natural regeneration on soil physicochemical properties. Records of soil attributes published in peer-reviewed journals from eight countries were collected. Clay content changed only in monoculture sites, decreasing 55.51% in the rhizosphere, while silt and sand presented significant variations in both monoculture and naturally regenerated areas. Conifers affected the soil more than broadleaved trees, evidenced by higher pH reduction (-2.96% vs. -1.98%) and higher increase of Al3+ (197.43% vs. 50.68%), K+ (80.40% vs. 69.90%), CEC (24.61% vs. 17.35%), and total organic carbon (82.21% vs. 69.89%). Also, the rhizosphere affected regeneration soils more than monoculture, indicated by higher Al3+ (50.68% vs. ns) and available P (32.31% vs. ns), K+ (203.44% vs. ns), CEC (34.90% vs. 20.93), and total organic carbon (91.55% vs. 63.23%). These results indicate higher nutrient availability in naturally regenerated than monoculture sites, as higher species diversity and better plant litter quality are expected. This meta-analysis shows that coniferous and naturally regenerated trees had a higher influence on the rhizosphere and soil properties than broadleaved and monocultures. Management practices must be revisited to ensure the long-term sustainability of forestry activity, and studies in tropical zones must be intensified.

Mitigating Lattice Distortion of High-Voltage LiCoO2 via Core-Shell Structure Induced by Cationic Heterogeneous Co-Doping for Lithium-Ion Batteries

HighlightsA simple two-step multi-element co-doping strategy is proposed to fabricate core-shell structured LiCoO2 based on the different diffusivities of dopant ions.The high diffusivity Al3+/Mg2+ ions occupy the core of single-crystal grain while the low diffusivity Ti4+ ions enrich the shell layer. In-situ XRD demonstrates the mitigated structural distortion under a high cut-off voltage of 4.6 V, resulting in a significantly improved cycling stability.

High-efficiency process of aluminum removal from rare earth solutions using a readily industrialized ionic liquid

Aluminum (Al) is often associated with rare earth resources, and the removal of Al3+ from rare earth elements (REEs) is a difficult task due to its amphoteric properties. Aluminum ions (Al3+) enrich in Sm3+-Gd3+ solution with the traditional 2-Ethylhexylphosphoric acid mono-2-ethylhexyl ester (P507)-kerosene-HCl system, emulsifying the phases, polluting the rare earth products and reducing the separation efficiency. A readily industrialized ionic liquid (IL) was synthesized with methyltrioctylammonium chloride ([N1888]Cl) and industrial naphthenic acid (NA) for the purification of Al3+ from GdCl3 solution. Under the experimental conditions, the extraction properties of diluted [N1888][NA], diluted NA and saponified NA were comparatively investigated and the separation factors (βAl/Gd) of Al/Gd were 23.0, 3.5 and 1.3, respectively. The effects of the salting-out agent, extraction agent, pH value and phase ratio on metal extraction efficiency were optimized. Finally, the industrial GdCl3 feed with a high Al3+ impurity of 889 mg/L was lowered to 5 mg/L. The removal efficiency of Al3+ was 99.4%, and the purity of Gd3+ was 99.998%. It provides a potential method for Al3+ purification from rare earth solutions with advantages of high efficiency, raw materials availability and ready industrialization.

Effects of Al3+ on the microbial community, metabolic pathways, and morphological analysis of activated sludge

Al3+ generated during aluminum mining, electrolytic industry, and aluminum-based coagulant production enters sewage treatment plants and interacts with activated sludge, interfering with microbial growth and community succession. An anaerobic-anoxic-oxic (A2O) process was used to investigate the effect of Al3+ on biological denitrification, the metal form, and the microbial community structure. The results showed that a low concentration of Al3+ improved removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) as well as biological activity. However, a high concentration of Al3+ reduced the COD and TN removal efficiencies. The removal efficiencies of COD, TN, and NH4+-N were the highest, and the INT-ETS values in the anaerobic, anoxic, and oxic zones were 93.21, 91.36, and 94.44 mg·INTF/(g·TSS·h) in the 10 mg/L Al3+ concentration treatment. Regardless of the change in Al3+ concentration, aluminum in the sludge mainly existed in the form of stable organic aluminum. Microbial richness and diversity decreased under the high concentration of Al3+. However, the relative abundance of Bacteroidetes and Chitinophagales increased, which was coincident with the change in microbial aluminum tolerance capacity. The dominant flora included Proteobacteria, Gammaproteobacteria, Betaproteobacteriales, Rhodocyclaceae, and Thauera. Amino acid and carbohydrate metabolism, as well as membrane transport and replication and repair, were the main metabolic pathways. K03088, K03406, and K02014 exhibited good adaptability under the high Al3+ concentration, which ensured effective removal of COD and TN.

Soil Chemical Properties as Affected by Tillage Method, Phosphorus and Lime Application

Continuous land degradation and soil acidity are some of the major causes of below optimal crop yields in Kenya. Sustainable crop production therefore calls for efficient soil health management strategies. Field experiments were carried out at Waruhiu Farmers Training Centre, Kiambu for two seasons to evaluate the effects of tillage methods, phosphorus and lime application on selected properties of acid soils. Ploughing, strip tillage and hand hoe tillage methods and, DAP + lime (DAPL), TSP + lime (LP), TSP (P) were evaluated. Burnt lime at 3.2 tones ha-1 rate was used as lime source while 52kg P ha-1 was used as Phosphorus source. Obtained data indicated that the soils were strongly acidic with high exchangeable Al3+ and Al saturation, low cation Exchange capacity (CEC) and available P. Combination of Ploughing, lime and phosphorus in form of TSP significantly (P ≤ 0.05) led to > 38% increase of soil pH, >75% extractable P, 51% exchangeable Ca, >60% CEC, 54% Exchangeable Mg and reduced Al concentrations by >83% compared to the control. Similarly, combination of ploughing, DAP and lime significantly (P ≤ 0.05) increased CEC by 42% and available P by 81% compared to control. DAPL was observed to significantly (P ≤ 0.05) promote higher levels of exchangeable Al Compared to control and LP in both seasons. Plough DAPL also increased available P by 49% compared to strip DAPL. Strip LP significantly increased Exchangeable Ca by 46% compared to control. Sole tillage methods did not significantly affect soil properties. It can, be concluded that integrating ploughing with either DAPL or LP improves the selected acid soil properties. There is however need for long term studies to understand long term effects of the fertilizer- lime -tillage methods interaction on soil acidity management.

Extreme low pH, not Al3+ , is a key abiotic stressor for the extremophyte Carex angustisquama (Cyperaceae) in highly acidic solfatara fields.

Volcanic acidification creates extreme soil conditions, where rhizotoxicity from extremely low pH (2-3) and high Al3+ strongly inhibit plant growth. C. angustisquama is a dominant extremophyte in highly acidic solfatara fields, where no other vascular plants can survive. Here we investigated the key abiotic stressor determining survival of this extremophyte. Soil analyses and topographic surveys were conducted to examine the effects of low pH and Al3+ , two major abiotic stressors in acidic soils, on the occurrence of C. angustisquama in solfatara fields. Hydroponic culture experiments were also performed to test its growth responses to these stressors. In field surveys, the spatial distribution of soil pH was consistent with vegetation zonation within a solfatara field. In contrast, soil exchangeable Al content was overall low due to strong eluviation. Statistical analysis also supported the significant role of soil pH in determining the distribution of C. angustisquama in a solfatara field. Furthermore, hydroponic culture experiments revealed a higher tolerance of C. angustisquama to low pH than a sister species, especially in the range pH 2-3, corresponding to the pH values of the actual habitats of C. angustisquama. Conversely, no significant interspecific difference was detected in Al3+ tolerance, indicating that both species had high Al3+ tolerance. This study suggests that low pH is a critical abiotic stressor leading to formation of the extremophyte in highly acidic solfatara fields. In contrast, C. angustisquama displayed high tolerance to Al3+ toxicity, probably acquired prior to speciation.

Water-Stabilized Vanadyl Phosphate Monohydrate Ultrathin Nanosheets toward High Voltage Al-Ion Batteries.

Al ion batteries (AIBs) are attracting considerable attention owing to high volumetric capacity, low cost, and high safety. However, the strong electrostatic interaction between Al3+ and host lattice leads to discontented cycling life and inferior rate capability. Herein, a new strategy of employing water molecules contained VOPO4 ·H2 O to boost Al3+ migration via the charge shielding effect of water is reported. It is revealed that VOPO4 ·H2 O with water lubrication effect and smaller steric hindrance owns high capacity and fast Al3+ diffusion, while the loss of unstable water upon cycling leads to a rapid performance degradation. To address this problem, ultrathin VOPO4 ·H2 O@MXene nanosheets are fabricated via the formed TiOV bond between VOPO4 ·H2 O and MXene. The MXene aided exfoliation results in enhanced VOwater bond strength between H2 O and VOPO4 that endows the obtained composite with strong water holding ability, contributing to the extraordinary cycling stability. Consequently, the VOPO4 ·H2 O@MXene delivers a high discharge potential of 1.8V and maintains discharge capacities of 410 and 374.8 mAh g-1 after 420 and 2000 cycles at the current densities of 0.5 and 1.0 A g-1 , respectively. This work provides a new understanding of water-contained AIBs cathodes and vital guidance for developing high-performance AIBs.

Synthesis and high sensitivity Al3+ recognition of fluorescent probe molecule based on pincer bis‐N‐heterocyclic carbene

Two bis-(Nitrogen-Heterocyclic Carbene, NHC) derivatives, 1, 3-bis[1-(quinolin-8-yl)-imidazolium-3-yl)]-benzene bis-hexafluorophosphate (2a), 2, 5-bis[1-(quinolin-8-yl)-imidazolium-3-yl)]-pyridine bis-hexafluorophosphate (2b), were synthesized, and characterized by 1H NMR and 13C NMR spectra and X-ray single crystal diffraction. The bis-NHC 2a was demonstrated as an excellent fluorescence chemo-sensor molecule for selectively recognition of Al3+ ion in aqueous-organic media. Its pyridine analogue molecule 2b haven't selectivity recognition character to metal ions with the fluorescence enhancement for most metal ions. A 1:1 binding ratio and strong supramolecular interaction between Al3+ ion and the carbonic hydrogen and quinoline nitrogen were suggested by Job's plot analysis and 1HNMR spectroscopy titrations of Al3+ ion and 2a. The detection limit for Al3+ ion was calculated to be 0.32 µM. The practical application in tap water samples has been evaluated, which reveals the potential applications of bis-NHC 2a in complicated environments.

Recent advances in developing organic positive electrode materials for rechargeable aluminum-ion batteries

Rechargeable aluminum-ion (Al-ion) batteries have been highlighted as a promising candidate for large-scale energy storage due to the abundant aluminum reserves, low cost, high intrinsic safety, and high theoretical energy density. However, the strong Coulombic interaction between the high charge density Al3+ and electrode host lattices leads to poor kinetics and insufficient cycle life in Al-ion batteries with inorganic electrodes. In contrast, organic electrode materials exhibit the advantages of designable molecular structure, flexible framework, coordinated energy storage chemistry, and resource sustainability. Nevertheless, organic materials encounter inherently high solubility, low active center utilization, and low electrical conductivity. Herein, the recent advances in developing organic positive electrode materials for Al-ion batteries is reviewed, and the charge storage mechanisms and electrochemical performances of different types of organic materials are systematically summarized. This review also discusses design strategies to improve specific capacity, operating voltage, cycle life, and rate capability of organic positive electrodes for Al-ion batteries. Finally, the challenges and research outlook toward high performance Al/organic batteries are presented.

Amorphous Silica‐Alumina as Suitable Catalyst for the Diels‐Alder Cycloaddition of 2,5‐Dimethylfuran and Ethylene to Biobased p‐Xylene

AbstractThe potential of amorphous silica‐alumina (ASA) to substitute zeolites (HBeta‐25) for the synthesis of p‐xylene via Diels‐Alder cycloaddition (DAC) of ethylene to 2,5‐dimethylfuran (2,5‐DMF) is investigated. ASA were prepared via homogeneous deposition‐precipitation of Al on SiO2. ASA shows good yields of p‐xylene (20–25 % after 18 hours) compared to bare silica and γ‐alumina. Brønsted acid sites (BAS) were identified as the active sites for the DAC reaction. The catalytic performance correlated strongly with the BAS concentration. Increasing the acidity of ASA is, however, limited by formation of agglomerated alumina‐type clusters at higher Al3+ content. While HBeta‐25 zeolite shows initially a slightly higher performance in terms of p‐xylene yield, ASA is the better catalyst upon calcination‐regeneration of the used catalyst. These results furthermore confirm that confinement in zeolite micropores is not a prerequisite for the DAC reaction between 2,5‐DMF and ethylene.

Management of Al3+ Residue in the Soil by Mapping Soil Capability in Retaining and Transporting Al3+ in the Farmland of Trang Bom District, Vietnam

The assessment of soil capability in retaining and transporting chemical substances is necessary, especially currently, with the overuse of chemical products for crop production. Depending on the soil properties, these chemicals may bound on soil particles or release and transport in the soil solution. In this study, we developed maps of the capability of soil to retain and transport Al3+, thereby evaluating the main soil factors affecting Al3+ fate in the agricultural land of Trang Bom District, Dong Nai Province, Vietnam. Information and data of the factors slope, soil texture, pH, organic matter, and ferrallitisation were processed and analyzed. The GIS tool was applied in combination with the analytical hierarchical process (AHP) to create the maps. Four hundred simulation runs were performed for criteria weight sensitivity analysis to explore the dependency of the resultant maps on the weights of the input factors. Sampling soil data were used to validate the accuracy of information given by the resultant maps. Results from the two maps show that the soils in the area have high capability in retaining and transporting Al3+. Ninety nine percent of the soils in the area have medium to high capability of Al3+ retention and about 65% of the soils have medium to high capability of transporting Al3+. For the agricultural land, about 65% of the land ranked as having a high to very high soil Al3+ retention capability and about 58% of the land ranked as having a medium to high capability of transporting Al3+. These maps can support the process of decision-making in identifying the appropriate dose and frequency of the chemical products that are applied on each soil capability zone; in this case study, the products contain aluminum. The accumulation of Al3+ in the soil, especially in the high Al3+ retention capability soil, can cause soil degradation and can cause negative effects on plant growth.

High lignin containing hydrogels with excellent conducting, self-healing, antibacterial, dye adsorbing, sensing, moist-induced power generating and supercapacitance properties

Herein, we design a dynamic redox system of using high contents of lignosulfonate (LS) and Al3+ to prepare poly acrylic acid (PAA) (LS-g-PAA-Al) hydrogels. The presence of high LS and Al3+ contents, in combination with the effective Al3+ complexes formed, renders the resultant hydrogel with some unique attributes, including excellent ionic conductivity (as high as 7.38 S·m−1) and antibacterial activity; furthermore, a very fast gelation (in 1 min) was obtained. As a flexible strain sensor, the LS-g-PAA-Al hydrogel with high conductivity demonstrates superior sensitivity in human movement detection. In addition, the rich anionic hydrophilic groups, such as sulfonic groups, phenolic hydroxyl groups, in the hydrogels impart the resultant hydrogels with excellent adsorption capacity for cationic dyes: when using Rhodamine B (RB) as a model cationic dye, the adsorption capacity of the resultant hydrogel reaches 334.64 mg·g−1; as a moist-induced power generator, it generates maximum 150.5 mV open circuit voltage with moist air flow. When the hydrogel electrolyte is assembled into a supercapacitor assembly, it shows high specific capacitance of 245.4 F·g−1, with the maximum energy density of 21.8 Wh·kg−1, power density of 2.37 kW·kg−1, and capacitance retention of 95.1% after 5000 consecutive charge-discharge cycles.

A facile strategy to synthesize high colour purity blue luminescence aluminium-doped CsPbBr3 perovskite quantum dots

Recently, metal halide perovskite materials (CsPbX3, X = Cl, Br, and I) have attracted extensive attention for designing optoelectronic devices owing to their tuneable bandgap and high photoluminescence quantum yields (PLQYs). However, the corresponding study of CsPbX3 perovskite quantum dots (QDs) with blue luminescence still lags far behind that of their red and green counterparts. Herein, we developed aluminium (Al3+) ion-doped CsPbBr3 perovskite QDs through a supersaturated recrystallization synthetic approach at room temperature. The crystal structure and optical properties of the as-prepared QDs were systematically characterized. The results reveal that the particle size and lattice spacing of Al3+ ion-doped CsPbBr3 QDs decrease as the Al/Pb molar ratio increases, which is attributed to the radius of Al3+ ions being much smaller than Pb2+ ions. A significant blueshift in the luminescence from 503 nm to 465 nm of Al3+ ion-doped QDs is observed as the Al/Pb molar ratio increases. Moreover, high colour purity (wide full-width at half-maximum of 83.3 meV) blue photoluminescence emission at 465 nm with a PLQY of 65.7% is achieved when the Al/Pb ratio reaches 1.0 in the Al3+ ion-doped CsPbBr3 QDs, which shows good stability under ambient atmosphere. These as-prepared high colour purity blue luminescence Al3+ ion-doped CsPbBr3 QDs show promising potential in blue optoelectronic fields.

Paleoenvironmental Conditions during the Paleocene–Eocene Transition Imprinted within the Glauconitic Giral Member of the Barmer Basin, India

The roughly 6 m thick limestone–green shale alternation within the lignite-bearing Giral Member of the Barmer Basin corresponds to a marine flooding event immediately after the Paleocene–Eocene transition. A detailed characterization of the glauconite using Electron Probe Micro Analyzer (EPMA), X-Ray Diffraction (XRD), Mössbauer and Field Emission Gun-Scanning Electron Microscope (FEG-SEM) reveals its origin in the backdrop of prevailing warm climatic conditions. The glauconite pellets vary from fine silt-sized to coarse sand-sized pellets, often reaching ~60% of the rock by volume. Mineralogical investigation reveals a ‘nascent’ to ‘slightly evolved’ character of the marginal marine-originated glauconite showing considerable interstratification. The chemical composition of the glauconite is unusual with a high Al2O3 (>10 wt%) and moderately high Fe2O3(total) contents (>15 wt%). While the K2O content of these glauconites is low, the interlayer sites are atypically rich in Na2O, frequently occupying ~33% of the total interlayer sites. The Mössbauer spectrum indicates 10% of the total iron is in ferrous form. High tetrahedral Al3+ of these glauconites suggests a high-alumina substrate that transformed to glauconite by octahedral Al-for-Fe substitution followed by the addition of K into the interlayer structure. The unusually high Na2O suggests the possibility of a soda-rich pore water formed by the dissolution of alkaline volcanic minerals. The Giral glauconite formation could have been a part of the major contributors in the Fe-sequestration cycle in the Early Eocene shelves. Warm climate during the Early Eocene time favored the glauconitization because of the enhanced supply of Fe, Al, and Si and proliferation of an oxygen-depleted depositional environment.

Fixed bed biosorption and ionic exchange of aluminum by brown algae residual biomass

This study aimed to evaluate the ion exchange and biosorption of Al3+ using as biosorbent material residual biomass generated in the alginate extraction process from the brown algae S. filipendula (named RES). The batch mode results showed that ion exchange, mainly with Na+ ions, has important participation in the removal of Al3+ ions by RES. Characterization analyses and blocking assays indicated that carboxylic, amino and sulfonate functional groups play a key role on the Al3+ biosorption. The dynamic system in a fixed packed bed column and the reuse/regeneration of the biosorbent was assessed by breakthrough method. Fixed bed experiments pointed that higher Al3+ removal was achieved at 0.5 mL/min and 1 mmol/L. DualSD model showed superior prediction of experimental data. Biosorption/Desorption cycles demonstrated the reuse feasibility of the biosorbent, which maintained a considerable adsorption capacity in all cycles performed.

Glauconite authigenesis during the onset of the Paleocene-Eocene Thermal Maximum: A case study from the Khuiala Formation in Jaisalmer Basin, India

Biological and ecological changes across the Paleogene hyperthermal events were accompanied by dramatic shifts in sedimentation systems in both marine and continental environments. This study investigates the formation of authigenic glauconite within a biostratigraphically constrained section encompassing the Paleocene-Eocene Thermal Maximum (PETM). Paleogene transgressive shelf deposits in the Jaisalmer Basin in western India are represented by the Khuiala Formation, consisting of grey shale, limestone, and glauconitic shale. Foraminiferal assemblage not only constrains the age of the glauconitic shale to planktic zone E1 but also indicates the deposition of sediments in an oxygen-depleted mid-shelf environment. A detailed geochemical and mineralogical characterization of the authigenic glauconite within the mid-shelf deposits reveals the highest glauconite content within the maximum flooding zone, immediately below the negative carbon isotope excursion representing the PETM, followed by its steady decrease. The geochemical signature of the glauconite is unusual for its high Al2O3 and MgO and medium Fe2O3 and SiO2 contents. The K2O content suggests the ‘evolved’ nature of the glauconite, which is confirmed by the X-ray diffractional parameters and the presence of the ‘rosette’ texture in FEG-SEM images. The glauconite evolved by Al-for-Fe substitution in the octahedral site and subsequent fixation of K+ into the interlayer sites. The high alumina content of the glauconite corresponds to the high Al3+ in the tetrahedral layer, inherited from an aluminous substrate. Mössbauer spectroscopy suggests the dominance of Fe3+ compared to Fe2+ in the octahedral site of glauconite pellets. The unusual variety of glauconite formed by the transformation of continent-derived kaolinite and iron oxide in oxygen-depleted porewater conditions. Glauconite authigenesis in the Khuiala Formation is strongly influenced by the warm climatic condition, oxygen-depletion in the mid-shelf environment, and sharp marine transgression promoting sediment starvation associated with the PETM.

A new genome allows the identification of genes associated with natural variation in aluminium tolerance in Brachiaria grasses.

Toxic concentrations of aluminium cations and low phosphorus availability are the main yield-limiting factors in acidic soils, which represent half of the potentially available arable land. Brachiaria grasses, which are commonly sown as forage in the tropics because of their resilience and low demand for nutrients, show greater tolerance to high concentrations of aluminium cations (Al3+) than most other grass crops. In this work, we explored the natural variation in tolerance to Al3+ between high and low tolerant Brachiaria species and characterized their transcriptional differences during stress. We identified three QTLs (quantitative trait loci) associated with root vigour during Al3+ stress in their hybrid progeny. By integrating these results with a new Brachiaria reference genome, we identified 30 genes putatively responsible for Al3+ tolerance in Brachiaria. We observed differential expression during stress of genes involved in RNA translation, response signalling, cell wall composition, and vesicle location homologous to aluminium-induced proteins involved in limiting uptake or localizing the toxin. However, there was limited regulation of malate transporters in Brachiaria, which suggests that exudation of organic acids and other external tolerance mechanisms, common in other grasses, might not be relevant in Brachiaria. The contrasting regulation of RNA translation and response signalling suggests that response timing is critical in high Al3+-tolerant Brachiaria.

The role of solute transporters in aluminum toxicity and tolerance.

The prevalence of aluminum ions (Al3+ ) under acidic soil conditions inhibits primary root elongation and hinders plant growth and productivity. Al3+ alters the membrane potential, displaces critical ions in the apoplast and disrupts intracellular ionic concentrations by targeting membrane-localized solute transporters. Here, we provide an overview of how Al3+ affects the activities of several solute transporters especially in the root. High Al3+ level impairs the functions of potassium (K+ ), calcium (Ca2+ ), magnesium (Mg2+ ), nitrate (NO3 - ) and ammonium (NH4 + ) transporters. We further discuss the role of some key transporters in mediating Al tolerance either by exclusion or sequestration. Anion channels responsible for organic acid efflux modulate the sensitivity to Al3+ . The ALUMINUM ACTIVATED MALATE TRANSPORTER (ALMT) and MULTIDRUG AND TOXIC COMPOUND EXTRUSION (MATE) family of transporters exude malate and citrate, respectively, to the rhizosphere to alleviate Al toxicity by Al exclusion. The ABC transporters, aquaporins and H+ -ATPases perform vacuolar sequestration of Al3+ , leading to aluminum tolerance in plants. Targeting these solute transporters in crop plants can help generating aluminum-tolerant crops in future.

Laser-based directed energy deposition of novel Sc/Zr-modified Al-Mg alloys: columnar-to-equiaxed transition and aging hardening behavior

The control of grain morphology is important in laser additive manufacturing (LAM), as grain morphology further affects the hot cracking resistance, anisotropy, and strength–ductility synergy of materials. To develop a solidification-control solution and achieve columnar-to-equiaxed transition (CET) in Al-based alloys during LAM, Sc-and-Zr-modified Al-Mg alloys were processed via directed energy deposition (DED). CET was achieved by introducing high potent primary Al3(Sc,Zr) nucleation sites ahead of the solidification interface. Furthermore, the relationship between the solidification control parameters and precipitation behavior of primary Al3(Sc,Zr) nucleation sites was established using the time-dependent nucleation theory. Then, the CET was studied according to the Hunt criterion. The results indicated that coarse columnar grain structure was still obtained at the inner region of the molten pool at low Sc/Zr contents owing to the effective suppression of the precipitation of the primary Al3(Sc,Zr) nucleation sites via rapid solidification during DED. In addition, the relatively low melt temperature at the fusion boundary unavoidably promoted the precipitation of primary Al3(Sc,Zr) nucleation sites, which resulted in a fine equiaxed grains band at the edge of the molten pool. As the Sc/Zr content increased, the solidification cooling rate was not sufficient to suppress the precipitation of the primary Al3(Sc,Zr) nucleation sites, and a fully equiaxed grain structure was obtained. Furthermore, the effect of the layer-by-layer manufacturing process on the subsequent precipitation strengthening of secondary Al3(Sc,Zr) precipitates was discussed. Both the remelting and subsequent aging during thermal cycling should be considered to achieve greater precipitation strengthening.

Effectiveness of innovative organic amendments in acid soils depends on their ability to supply P and alleviate Al and Mn toxicity in plants

Soil acidity with high Al3+ and Mn2+ is one of the major constraints to global food production. Lime is effective to increase soil pH, but it is not always readily available and can be expensive. This study aimed to evaluate the effectiveness of organic amendments that may be viable for treating soil acidity. Thirteen organic amendments (including manures, composts, biochars and plant residues) were added (1% soil weight) to two acid soils differing in pH buffer capacity, and Al3+ and Mn2+concentrations. They included a Dermosol with a pHCaCl2 of 4.1 and a Sodosol with pHCaCl2 of 4.0. Four inorganic amendments (lime, dolomite, gypsum, and KH2PO4) were included for comparison. The Al-sensitive wheat ES8 was grown for 49 days. Organic amendments (manures, composts, biosolids and biochars) outperformed or matched the shoot biomass response to lime in both soils. The most effective treatments were poultry litter, poultry-litter-biochar and biosolids, which increased shoot biomass by 128%, 158% and 95% for the Dermosol and by 58%, 43% and 33% for the Sodosol, respectively, compared with the limed controls. Organic amendments increased soil pHCaCl2 by up to 0.32 and 0.62 units and Olsen-P concentration by 16.1 μg g−1 and 30.7 μg g−1 for the Dermosol and Sodosol, respectively. Shoot biomass correlated positively with Olsen-P (R2 = 0.85) but negatively with concentrations of extractable Mn (R2 = 0.62) and Al (R2 = 0.58). Organic amendments were effective ameliorants for soil acidity. Their effectiveness depends on their ability to supply nutrients, primarily phosphorus, and to overcome Al3+ and Mn2+ toxicities.