Fe Grains Research Articles

Effect of alloying elements on zinc-induced liquid metal embrittlement in steels: A first-principles study

Liquid metal embrittlement (LME) induced by Zn melt in galvanized steels during spot-welding poses a significant challenge to the advancement of the automotive industry. A critical strategy to address this challenge is identifying promising alloying elements capable of mitigating LME. High-throughput first-principles calculations were employed to investigate the segregation behavior of 22 common alloying elements at the Σ5(310) grain boundary of iron and their impact on the grain boundary energy. The results indicate that volume distortion upon doping of the alloying elements predominantly influences their segregation behavior, while the weak bonding between Zn and Fe is responsible for the grain boundary embrittlement. Exploration of solute interaction between Zn and the other alloying element in the Fe grain boundary model reveals that the attraction between metallic doping elements and Zn correlates with both the elastic effects and the magnetic properties of the dopant, while the repulsion between non-metallic elements and Zn is primarily governed by the elastic effects. Separating the grain boundary strengthening energy into mechanical and chemical contributions shows that they correlate linearly with variations in volume of the doping site and changes in bond energy for bonds associated with the doping site at the grain boundary, respectively. Accordingly, the strengthening effect of the doping elements can be estimated by evaluating the induced changes in local volume and bond energies on grain boundaries. Furthermore, potential alloying elements to mitigate the Zn-induced LME are screened and discussed, with B and Mo being the most promising candidates.

Development of Fe‐10% (HA/β‐Tricalcium Phosphate) Composite via Solid‐State Manufacturing Route and Investigation of Material Properties for Biodegradable Implant Applications

Day‐by‐day biodegradable alloys and composites are getting more attention. Besides their competing material properties with traditional permanent implants, their harmless degradation in the body eliminates the need for a second surgery to remove the implant. Beyond other biodegradable materials such as Mg and Zn, Fe is known with high strength with low degradation rate. However there is still need to improve its biocompatibility. Herein, a Fe‐based composite is developed via solid‐state manufacturing route. 10% HA/β‐TCP is selected as an additive which is a biocompatible ceramic material and the powder mix is ball‐milled. Afterward, the powders are consolidated via high‐pressure torsion (HPT) with 1–5–10 revolutions at room temperature. Crack‐free structures are obtained even after 1 HTP rotation. Fe is in lamellar form around HA‐βTCP particles. With the increase of HPT rotation numbers, lath thickness decreased. After 10 HPT rotations, 24% enhancement in density is observed that points to a more condensed structure. Transmission electron microscopy observations show significant grain refinement after 1 HPT rotation, and Fe grain size remains constant (≈300 nm) up to 10 turns. Ultimate tensile strength increases while degradation rate decreases after 5 HPT rotations. This study provides the potential of enhanced Fe‐based biomaterials for thinner and smaller implant designs.

Improving Mechanical Properties of the Fe/epoxy Composite with a Novel Room Temperature-Thermal Curing Process

A novel room temperature-thermal curing process was proposed to fabricate the Fe/epoxy composite easily and rapidly. The effect of thermal curing on the microstructure and mechanical properties were investigated. The results show that the thermal curing leads to the coarsening of Fe phase and the dense of Fe/epoxy interface. The average diameter of Fe increased from 36.03 μm to 64.91 μm after thermal curing, leading to the microstructure evolved from the island shape to the quasi reticular structure. The voids in the Fe phase and cracks along the phase boundary in the Fe/epoxy composite disappeared under the effect of diffusion. The tensile strength increased from 13.14 MPa to 53.72MPa and the elongation increased from 5.86% to 8.18% after thermal curing, with the improvement of 308.8% and 39.6%, respectively. The combination of brittle fracture in Fe and the crack elongation along the interface of Fe/epoxy improve both the strength and the plasticity of the Fe/epoxy composite. The Fe grains sustain fine with average size of 0.49 μm, contains abundant low-angle grain boundary (LAGBs) and deformed grains, but the density of dislocation and the value of texture are extremely low.

High-pressure phase transitions in a laser directed energy deposited Fe-33Cu Alloy

Additively manufactured Fe-Cu alloys contain both equilibrium face-centered cubic (FCC) and metastable body-centered cubic (BCC) crystal structure Cu precipitates depending on their size. However, the stability of these nanoscale precipitates under extreme conditions such as high pressures has not been reported. This study investigates the phase transformations and microstructural stability of laser directed energy deposition (DED-LB) made Fe67Cu33 alloy (nominal composition in at.%) under high static pressure deformation using in-situ synchrotron X-ray diffraction under pressure, postmortem high-resolution scanning transmission electron microscopy (HR-STEM), and molecular dynamics (MD) simulations. In-situ XRD results reveal a reversible phase transformation from BCC to the hexagonal close-packed (HCP) structure in the Fe grains at an onset pressure of 16.4 GPa, significantly higher than reported in the literature for pure Fe. Although no high-pressure phase transition was observed in the FCC Cu grains through XRD, HR-STEM analysis uncovers a phase transition to the HCP structure in nanoscale metastable BCC Cu precipitates within the BCC Fe matrix. After decompression, the Fe matrix reverted back to the BCC structure with periodic lath martensite, while regions of the nanoscale BCC Cu precipitates retained the metastable HCP structure. MD simulations support the BCC → HCP transition in the embedded nanoscale coherent Cu precipitates, consistent with the classical Burgers mechanism. Thus, by leveraging in-situ XRD observation, postmortem high-resolution S/TEM microscopy, and MD simulations, this study offers profound insights into the distinctive phase transformations induced by high pressure in DED-LB Fe67Cu33 alloy, which is distinguished by its hierarchical microstructure.

Grain and shoot iron (Fe) content and root phytosiderophore release are the major determinants of Fe-deficiency tolerance index (FeDTI) and the reliable screening markers to breed Fe-efficient rice (Oryza sativa L.)

There is a need to exploit the genetic variability in rice to improve the Fe deficiency tolerance, particularly under aerobic conditions, and to improve the Fe uptake and accumulation in the grain to facilitate biofortification. The present research was conducted to ascertain the regulators and determinants of Fe-deficiency tolerance in rice. Fifty-seven diverse genotypes were investigated under Fe-deficient (1 µM, FDS, -Fe) and Fe-sufficient (100 µM, FSS, +Fe) nutrient solution cultures for growth and physiological attributes, Fe uptake and accumulation and root release of phytosiderophores (PS), etc., and Fe-deficiency tolerance index (FeDTI). A strong positive correlation was observed between root traits and the PS release. Further, a higher release of PS was evidenced as a major determinant of shoot Fe and grain Fe in rice particularly under Fe deficiency. Based on FeDTI, a total of ten rice genotypes were identified, and their Fe deficiency response was further validated on Fe deficient (∼2.1 ppm Fe, FeDS) and Fe-sufficient soils (∼10 ppm Fe, FeSS) in pot culture. Maintenance of high active Fe content and consequently a higher leaf chlorophyll content throughout the plant growth were extremely important determinants of grain yield and grain Fe fortification in rice under Fe deficiency than under the Fe sufficient condition. Based on the FeDTI, this study further identifies the Fe-deficiency tolerant rice genotypes which can be exploited through conventional and molecular breeding approaches to improve the Fe uptake efficiency and grain Fe content of the high-yielding rice genotypes.

Additive manufacturing of multi-materials with interfacial component gradient by in-situ powder mixing and laser powder bed fusion

Defects (e.g., pores and cracks) and high stress concentration derived from the significant mutation in materials are the critical challenge for multi-material structures fabricated by laser powder bed fusion (LPBF). Introducing a transition zone between dissimilar materials with a composition gradient at the interface may be a promising approach to resolve or minimize these problems. In this work, three distinct CuSn10 copper alloy (CuA)/316 L stainless steel (SS) multi-material gradient structures (i.e., CS, SC-1, and SC-2) were fabricated by a LPBF system with in-situ powder mixing and feeding capability. A buffer layer material based on the mixture of the two base materials was introduced at the interface between CuA and SS. The effects of the building strategies and interfacial composition gradient transition paths on the interfacial bonding characteristics were investigated. The microstructure evolution and the underlying interfacial bonding mechanisms were discussed. It was found that the interfacial bonding behaviors were critically dependent on the occurrence of liquid metal embrittlement induced by Cu penetration into Fe grains, as well as the width and microstructure gradient of the diffusion zone and high stress concentration at the interface. A non-uniform melting behavior of CuA and SS powders could be induced by the distinct thermal-physical properties between the two materials, which could lead to lack-of-fusion pores at the interface. In the CS sample, printing SS on the CuA with a buffer layer material could inhibit the formation of Cu-penetration cracks and increase the width of the diffusion zone, which may enhance the interfacial metallurgical bonding. This work may enhance the essential comprehension of improving interfacial bonding strength of LPBF-processed multi-material structures.

An In Situ Study of the Role of Pressure on Fe Recrystallization and Grain Growth During Thermomechanical Processing

An In Situ Study of the Role of Pressure on Fe Recrystallization and Grain Growth During Thermomechanical Processing

Effects of Fe, Si, Cu, and TiB2 Grain Refiner Amounts on the Hot Tearing Susceptibility of 5083, 6061, and 7075 Aluminum Ingots

Aluminum alloys 5083, 6061, and 7075 are prone to hot tearing under direct-chill casting conditions; the defects that form during solidification of those alloys are highly sensitive to variation in the alloying elements, with these elements commonly being Si, Fe, Cu, and Ti. This study investigates the influence of the morphology, content, and size of intermetallic compounds on the hot tearing behavior of the 5083, 6061, and 7075 aluminum alloys by combining a constrained rod casting technique, phase diagram calculation, and multiscale microstructural characterizations. The fishbone-shaped α-Al15(Fe,Mn)3Si2 in 5083 can serve as a path for crack nucleation and growth, and an increase in Si content results in Mg2Si assuming fishbone morphology, thereby increasing hot tearing susceptibility. The amount of plate-like β-Al5FeSi is the primary factor controlling the hot tearing susceptibility of 6061. For 7075, increasing the Cu content can greatly enhance the remaining liquid fraction, feeding, and hot tearing susceptibility. For all three alloys, TiB2 grain refiner minimizes hot tearing. This study elucidates the influences of the amounts of Fe, Si, Cu, and TiB2 grain refiner on hot tearing susceptibility. The findings can help establish compositional control standards for the 5083, 6061, and 7075 aluminum alloy series, particularly when the recycling rate must be increased.

Giant segregation transition as origin of liquid metal embrittlement in the Fe-Zn system

A giant Zn segregation transition is revealed using CALPHAD-integrated density-based modeling of segregation into Fe grain boundaries (GBs). The results show that above a threshold of only a few atomic percent Zn in the alloy, a substantial amount of up to 60 at.% Zn can segregate to the GB. We found that the amount of segregation abruptly increases with decreasing temperature, while the Zn content in the alloy required for triggering the segregation transition decreases. Direct evidence of the Zn segregation transition is obtained using high-resolution scanning transmission electron microscopy. Base on the model, we trace the origin of the segregation transition back to the low cohesive energy of Zn and a miscibility gap in Fe-Zn GB, arising from the magnetic ordering effect, which is confirmed by ab-initio calculations. We also show that the massive Zn segregation resulting from the segregation transition greatly assists with liquid wetting and reduces the work of separation along the GB. The current predictions suggest that control over Zn segregation, by both alloy design and optimizing the galvanization and welding processes, may offer preventive strategies against liquid metal embrittlement.

Characterization of 14 Triticum species for the NAM-B1 gene and its associated traits.

Wheat grain protein, zinc (Zn), and iron (Fe) content are important wheat qualities crucial for human nutrition and health worldwide. Increasing these three components simultaneously in wheat grains by a single gene came into the picture through NAM-B1 cloning. NAM-B1 gene and its association with the mentioned grain quality traits have been primarily studied in common and durum wheat and their progenitors T. dicoccum and T. dicoccoides. In the present study, for the first time, 38 wheat accessions comprising ten hexaploids from five species and 28 tetraploids from nine species were evaluated in the field for two consecutive years. Additionally, the 582 first nucleotides of the NAM-B1 gene were examined. The NAM-B1 gene was present in 21 tetraploids and five hexaploid accessions. Seven tetraploid accessions contained the wild-type allele (five T. dicoccum, one T. dicoccoides, and one T. ispahanicum) and fourteen the mutated allele with a 'T' insertion at position 11 in the open reading frame, causing a frameshift. In hexaploid wheat comprising the gene, only one accession of T. spelta contained the wild-type allele, and the rest resembled the insertion mutated type. In the two-year field experiment, eight accessions with the wild-type NAM-B1 allele had significantly higher protein, Zn and Fe grain content when compared to indel-type accessions. Additionally, these accessions exhibited a lower mean for seed-filling duration than all other accessions containing indel-type alleles. In terms of grain yield, 1,000-kernel weight, kernel diameter, and kernel length, T. dicoccum accessions having wild-type alleles were similar to the indel-type accessions over two years of evaluation. These findings further support the possibility of simultaneous improvement of wheat grain protein, Zn, and Fe content by a single gene crucial for human nutrition and health worldwide.

Exploring the linkage between root system architecture and grain iron content in wheat (Triticum aestivum L.)

Iron (Fe) is a vital element that is equally important for plants, animals, and humans. High Fe concentrations in wheat grains have reliance on plant roots, the hidden half of the plant with a role in nutrient mining. Enhanced grain Fe content of wheat can positively mitigate Fe malnutrition in poor populations. In the present study, 100 wheat varieties were studied to identify the root architectural characteristics in relation to grain Fe concentration. Germinated seeds were transplanted in a rhizobox kept in a standard nutrient solution and were harvested 12 days after transplanting. Roots were scanned and the images were processed using smart root software. A total of 12 wheat varieties, which had a vigorous and weak root system architecture (RSA), in combination with higher and lower Fe grain concentrations, were selected using principal component analysis. The uptake and translocation of Fe from root to shoot were determined through a pot experiment conducted for the above-mentioned 12 wheat varieties, with or without Fe fertilizer applied as FeSO4 to the soil. The data obtained from the pot experiment revealed that Dharabi-11 with vigorous RSA exhibited the highest grain Fe concentration (57.20 mg kg−1), low phytate concentration (6.50 mg kg−1), and maximum 1,000 grain weight, whereas Ujala-16 with weaker RSA had the lowest grain Fe concentration (13.33 mg kg−1), highest phytate concentration (9.07 mg kg−1), and lowest 1,000 grain weight. There were also varieties showing higher grain Fe concentrations with weaker RSA and vice versa. Although it is indicated that vigorous RSA leads to high grain Fe concentration, it is not the sole factor in high grain Fe concentration. Nevertheless, the results demonstrate that large genetic diversity is available among indigenous wheat germplasm in terms of grain Fe concentration and RSA. This information may be utilized in the development of new varieties through conventional and marker-assisted breeding programs using RSA traits for Fe biofortification in wheat, leading to the mitigation of Fe malnutrition.

Phenotypic and genetic diversity of doubled haploid bread wheat population and molecular validation for spike characteristics, end-use quality, and biofortification capacity.

Increasing grain quality and nutritional value along with yield in bread wheat is one of the leading breeding goals. Selection of genotypes with desired traits using traditional breeding selection methods is very time-consuming and often not possible due to the interaction of environmental factors. By identifying DNA markers that can be used to identify genotypes with desired alleles, high-quality and bio-fortified bread wheat production can be achieved in a short time and cost-effectively. In the present study, 134 doubled haploid (DH) wheat lines and their four parents were phenotypically evaluated for yield components (spike characteristics), quality parameters, and grain Fe and Zn concentrations in two successive growing seasons. At the same time, ten genic simple sequence repeats (SSR) markers linked to genes related to the traits examined were validated and subsequently used for molecular characterization of trait-specific candidate genotypes. Significant genotypic variations were determined for all studied traits and many genotypes with desired phenotypic values were detected. The evaluation performed with 10 SSR markers revealed significant polymorphism between genotypes. The polymorphic information content (PIC) values of 10 markers ranged from 0.00 to 0.87. Six out of 10 SSRs could be more effective in representing the genotypic differentiation of the DH population as they demonstrated the highest genetic diversity. Both Unweighted Pair Group Method with Arithmetic Mean (UPGMA) clustering and STRUCTURE analyses divided 138 wheat genotypes into five (K = 5) main groups. These analyzes were indicative of genetic variation due to hybridization and segregation in the DH population and the differentiation of the genotypes from their parents. Single marker regression analysis showed that both Xbarc61 and Xbarc146 had significant relationships with grain Fe and Zn concentrations, while Xbarc61 related to spike characteristics and Xbarc146 related to quality traits, separately. Other than these, Xgwm282 was associated with spike harvest index, SDS sedimentation value and Fe grain concentration, while Gwm445 was associated with spikelet number, grain number per spike and grain Fe concentration. These markers were validated for the studied DH population during the present study and they could be effectively used for marker-assisted selection to improve grain yield, quality, and bio-fortification capacity of bread wheat.

Forming super-Mercuries: Role of stellar abundances

Rocky exoplanets with bulk iron mass fraction of more than 60%, known as super-Mercuries, appear to be preferentially hosted by stars with higher iron mass fraction than that of the Sun. It is unclear whether these iron-rich planets can form in the disc or whether giant impacts are necessary for their formation. Here, we investigate the formation of super-Mercuries in their natal protoplanetary discs by taking into account their host stars’ abundances (Fe, Mg, Si, and S). We employed a disc evolution model which includes the growth, drift, evaporation, and recondensation of pebbles to compute the pebble iron mass fraction. The recondensation of outwardly drifting iron vapour near the iron evaporation front is the key mechanism that facilitates an increase in the pebble iron mass fraction. We also simulated the growth of planetary seeds around the iron evaporation front using a planet formation model which includes pebble accretion and planet migration and we computed the final composition of the planets. Our simulations were able to reproduce the observed iron compositions of the super-Mercuries, provided that all the iron in the disc are locked in pure Fe grains and that the disc viscosity is low (α ~ 10−4). The combined effects of slow orbital migration of planets and long retention time of iron vapour in low-viscosity discs makes it easier to form iron-rich planets. Furthermore, we find that decreasing the stellar Mg/Si ratio results in an increase in the iron mass fraction of the planet due to a reduction in the abundance of Mg2SiO4, which has a very similar condensation temperature as iron, in the disc. Our results imply that super-Mercuries are more likely to form around stars with low Mg/Si (≲ 1), in agreement with observational data.

Effects of Alloying Elements on the Solution and Diffusion of Oxygen at Iron Grain Boundary Investigated by First-Principles Study

The effects of alloying elements (Si, Cr, Mo) on the solution and diffusion of oxygen (O) atoms at the grain boundary of iron (Fe) Σ5(310)/[001] are investigated by the simulations of ab initio density functional theory (DFT). It is found that Si, Mo and Cr prefer to segregate to the grain boundary, and further affect the solution and diffusion of O atoms at Fe grain boundaries. The segregated Cr promotes the solution of O, while Si and Mo inhibit the solution of O at the grain boundary. Meanwhile, Cr and Si accelerate the diffusion of O, and Mo retards the diffusion of O in the grain boundary. Further analysis indicates that the effects are closely related to the interactions between the alloying elements and O atoms, which are determined by the competition between the distortion of local structure and the charge transfer between local atoms. Finally, the effects of alloying elements on the O concentration distribution near the grain boundary are explored by employing the Langmuir–McLean models. This work not only provides insights into the effects of alloying elements on the solution and diffusion of O at grain boundaries, but also provides parameters of the atomic interactions for the initial oxidation simulation on a large scale, which relates to the growth of oxide in polycrystalline systems with various grain sizes at experimental temperatures.

Genotype by Environment Interaction in Grain Iron and Zinc Concentration and Yield of Maize Hybrids under Low Nitrogen and Optimal Conditions.

Maize is the staple food crop for millions of people in sub-Saharan Africa. Iron (Fe) and zinc (Zn) deficiency is a significant health risk that mainly affects low-income populations who rely solely on maize-based diets. This problem can be alleviated by developing micronutrient-rich maize grain. The aim of this study was to determine the adaptation and performance of hybrids for Fe and Zn concentration and grain yield under low soil nitrogen (N) and optimal conditions. Eighteen hybrids derived from lines and testers with low, medium, and high Fe and Zn concentration were grown during the summer rainy seasons of 2017 and 2018 at three locations under low and optimal N conditions. There were significant genotype and environment effects for grain yield, and Fe and Zn concentration, but the genotype by environment interaction effects were the largest, accounting for between 36% and 56% of variation under low N conditions. Low N levels significantly reduced grain yield, and Fe and Zn concentration. Hybrids G1, G2, G4, G7, G10, G11, and G16 were relatively stable, with relatively high mean Fe and Zn concentrations, and low additive main effects and multiplicative interaction (AMMI) stability values and iron stability index (FSI) and zinc stability index (ZSI) under low N conditions. These genotypes can be considered for production under low N stress conditions. Two environments (E4 and E3) were identified for good discriminatory power for genotype performance in terms of Fe and Zn content, respectively. Stable and high-yielding genotypes with high Fe and Zn concentration can be used as biofortified hybrids, which can contribute to a sustainable solution to malnutrition in the region, especially under low N conditions.

Study and Characterization of Fe3O4-PEG Nanoparticles Using The Co-Precipitation Method For The Production of Permanent Magnets

Natural iron sand is one of the natural resources in Indonesia, especially in the Cianjur area, West Java which has been used optimally. This study aims to analyze Fe's content, properties, and grain size found in Cianjur, West Java. The natural iron sand samples were prepared using the calcination method, which was dried at 50°C until the samples became powder. Beach sand samples are extracted using a permanent magnet to separate magnetic and non-magnetic materials. Characterization of iron sand using XRD, SEM, VSM, and FTIR. The XRD results show that the natural iron sand sample has a single magnetite phase (Fe3O4). A spinel cubic crystal structure is formed with lattice parameters of 8,513 Ǻ using Co-Precipitation. SEM results show that the sample is inhomogeneous or homogeneous, as indicated by the gap and agglomeration of particles in each sample. VSM results show that the parameter magnetic properties saturation (Ms) on average is 23.9763735 emu/g, magnetic remanence (Mr) is on average 5.14865198 emu/g, and coercivity is on average 125.139457033 emu/g. Where in sample 1, saturation is 29.7729509 emu/g, remanance is 4.0486018 emu/g, coercivity is 92.1368641 emu/g, sample 2 is saturation 21.5994425 emu/g, remanance 8.18772602 emu/g, coercivity 179.567079 emu/g and sample 3 has a saturation value of 20.55672771 emu/g, remanance 3.20962812 emu/g. Then, the FTIR results showed a shift in the vibration peak, which experienced a change in the vibrational energy of Fe-O and then showed the -OH group at an absorption of 3400/cm. The results of this study have the potential to process other magnetic materials.

Interface selection behavior during the growth of δ-Fe grains in liquid Cu

In this study, the selection process of low-energy grain boundaries of δ-Fe grains (>25 μm) suspended in the liquid copper was studied based on the characteristics of Cu-Fe monotectic alloy which suggests that liquid Cu-rich phase and solid Fe grains can coexist over a wide temperature range. The distribution of grain boundaries was analyzed by EBSD, and it was found that Σ3 and Σ9 high angle grain boundaries with low energy were preferentially formed between δ-Fe grains at 1100 and 1150 °C. After heat treatment at 1200 °C, the δ-Fe grains agglomerated into a spherical shape with a ``bud'' structure, in which Σ1 grain boundaries dominated. Thus, the selective attachment of low-energy interfaces between floating grains in the liquid phase was elucidated.

Combining ability and heterosis studies for grain iron and zinc concentrations in pearl millet [Cenchrus americanus (L). Morrone

Iron (Fe) and zinc (Zn) deficiency has been identified as a major food-related health issue, affecting two billion people globally. Efforts to enhance the Fe and Zn content in food grains through plant breeding are an economic and sustainable solution to combat micronutrient deficiency in resource-poor populace of Asia and Africa. Pearl millet, Cenchrus americanus (L). Morrone, considered as a hardy nutri-cereal, is the major food crop for millions of people of these nations. As an effort to enhance its grain mineral content, an investigation was conducted using line × tester analysis to generate information on the extent of heterosis, gene action, combining ability for grain yield potential, and grain mineral nutrients (Fe and Zn). The partitioning of variance attributable to parents indicated that the lines and testers differed significantly for the traits studied. For most of the attributes, hybrids that were superior to the parents in the desired direction in terms of per se performance were identified. The analysis of combining ability variance indicated the preponderance of both additive and non-additive genetic effects. Thus, reciprocal recurrent selection can be used to develop a population with high-grain Fe and Zn contents. The Fe and Zn content in grain exhibited a highly significant and positive association between them, whereas the Fe and Zn contents individually showed a negative, albeit weak, correlation with grain yield and a moderate positive relation with grain weight. This indicates that mineral nutrient contents in grains can be improved without significant compromise on yield. The consistency of these trends across the environment suggests that these findings could be directly used as guiding principles for the genetic enhancement of Fe and Zn grain content in pearl millet.

How Much Phosphorus Uptake Is Required for Achieving Maximum Maize Grain Yield? Part 2: Impact of Phosphorus Uptake on Grain Quality and Partitioning of Nutrients

Previous studies have shown that excess phosphorus (P) uptake by maize can lead to a decreased grain yield. Part one of this study demonstrated that maize experienced luxury consumption of P in three phases of P uptake. The objective of this work was to further explore how P uptake indirectly impacts the uptake of other nutrients and their translocation within the plant to explain the yield penalty associated with luxury P consumption. Three maize hybrids were grown under optimal conditions using sand-culture hydroponics for precise control of the root environment. Plants were grown to maturity with six different P concentrations followed by biomass and nutrient partitioning analysis of various maize parts. All non-P nutrients achieved maximum grain content at P uptake levels that coincided with the maximum grain yield, while the partitioning of K, Mg, Mn, B, N, S, and Fe into other non-grain tissue continued with further P uptake. With luxury P consumption beyond the point corresponding with maximum grain yield, the N, S, Fe, Cu, and Zn grain content significantly decreased along with the grain yield. With luxury P consumption, Cu, Zn, and Fe accumulated in the roots. Grain production with luxury P uptake may have been limited by P-inhibited translocation of Cu, Zn, and Fe from roots to grain. This decrease in translocation did not prevent further non-grain tissue growth since those nutrients were not as limiting as they were for grain. Data suggest that these micronutrients limited protein production, which was evident from the decrease in grain N and S content and concentration that coincided with the decrease in grain yield concomitant with luxury P uptake.

Grain growth and segregation in Fe-doped SrTiO3: Experimental evidence for solute drag

In functional ceramics, the impact of dopants on bulk crystals is generally well understood. Their impact on grain boundaries is less well known. The present study investigates the impact of acceptor dopants on grain growth in strontium titanate. Scanning electron microscopy and analytical (scanning) transmission electron microscopy have been used to gain knowledge on Fe segregation behavior, grain sizes, and grain size distributions of SrTiO3. While undoped microstructures show normal grain growth at low temperatures (<1350 °C), doped microstructures evolve bimodally. With increasing acceptor dopant concentration, an increasing population of small grains develops. It is shown that Fe segregates to the grain boundaries due to its negative charge and a positive boundary potential. Thus, the experimental findings seem to be well explained by the theory of solute drag: The diffusion of segregated defects (‘solutes’) at grain boundaries can retard grain boundary migration.