Homogeneous Composition Research Articles

Impact of Laser Remelting Parameters on the Microstructure and Properties of Sprayed Ni20Cr Coatings with Rhenium Addition

The study was focused on the characterization of microstructural evolution and microhardness in the plasma-sprayed and laser remelted Ni-Cr coatings with 20% addition of rhenium on stainless steel. The remelting process was performed with different laser power and laser traverse speed. The laser remelting process improves the quality of plasma sprayed Ni-Cr-Re coatings, reducing the porosity and the inhomogeneity of the chemical composition. The remelted coatings were characterized by a dendritic microstructure. Microsegregation of rhenium to dendrites was observed. The remelted coatings have an iron content of over 40%, which is the result of too deep remelting with the substrate material. The iron content in the remelted coatings increases with the decrease in laser speed, but the rhenium content decreases. All tested coatings were characterized by hardness similar to that of the substrate material.

A hierarchically porous and SLIT3-releasing scaffold for bone tissue engineering applications

AbstractOne of the most fundamental characteristics of a biomaterial tailored for bone repair and regeneration is its ability to promote bone regeneration and healing of large defects. This work reports producing a functionalized and hieratically porous bone scaffold that significantly supports cell adhesion and proliferation by providing bone mimicry structure and controlled release of protein. The Slit Guidance Ligand 3 (SLIT3) protein was previously tested to promote bone formation and control the resorption process in natural bone healing. In this study, our goal was to design a nanocomposite bone scaffold to be functionalized with SLIT3 protein and then evaluate the uptake and release profile from surface into culture media to support bone marrow-derived mesenchymal stem cells (MSC) 3D culture. Indirect 3D printing of a polylactic-co-glycolic acid (PLGA), hydroxyapatite nanoparticles, and polydopamine coated (PLGA-HANPs-PDA) was utilized to obtain a hierarchically porous and SLIT3 protein-releasing scaffold. The produced scaffold was evaluated and optimized using chemical, architectural, mechanical, and biological characterization techniques. Optimal physicochemical properties resulted in a unique microstructure with an average pore size of 178.06 ± 45 µm, 63% porosity, and stable and homogenous chemical composition. Mechanical testing demonstrated a compression strength up to 1.5 MPa at 75% strain, with a compression modulus of 0.58 ± 0.05 MPa. Preliminary biological experiments showed that the scaffold exhibited gradual SLIT3 protein release, biodegradability, and reliable biocompatibility for MSC cell culture. Finally, we showed for first time the bioactivity of SLIT3 protein within PLGA-HANPs-PDA scaffold to promote attachment and growth of mesenchymal stem cell (MSCs) seeded in bone mimicry scaffold matrix. The collected findings will serve as a bedrock for thorough and targeted in vitro studies to evaluate anticipated osteogenesis the MSCs.

Regulating the Intralayer Cation Disorder in Layered Lithium-Rich Cathodes to Improve Cycle Performance.

The Li/Mn ordered structure of lithium-rich (LR) cathodes leads to the heterogeneous Li2MnO3 and LiTMO2 components, readily triggering structural degeneration and performance degradation in long-term cycling. However, the lack of guiding principles for promoting cation disorder within the transition metal (TM) layers has posed a persistent challenge in designing homogeneous layered LR cathodes. Herein, the (Li + Mn)TM content in the TM layer as a criterion for the design of cation-disordered layered LR cathodes is proposed. The intralayer cation disorder can be achieved by tuning the (Li + Mn)TM content less than 0.5 combined with incorporating the solute ions with suitable ionic radii. For a multicomponent LR nickel cobalt manganese (LRNCM) oxides system, multiscale structural analyses reveal that cation-disordered layered Li1.1(Ni0.6Co0.1Mn0.3)0.9O2 (LR613) exhibits enhanced compositional homogeneity and higher R m symmetry. The developed LR613 cathode undergoes a solid-solution reaction during Li+ deintercalation and mitigates voltage decay during cycling. It is elucidated that intralayer cation disorder effectively alleviates microstrain within the cathode structure and enhances overall structural stability. This comprehensive understanding of the composition-structure-electrochemical behavior relationship inspires the development of durable cation-disordered layered LR cathodes through composition tuning.

Identification of Multiple Thermal Events in High‐Grade Metacarbonate Rocks Using Carbon Isotope Thermometry: An Example From the Sør Rondane Mountains, East Antarctica

ABSTRACTNine metacarbonate layers from the regionally metamorphosed terrane of the Sør Rondane Mountains in the Eastern Dronning Maud Land in East Antarctica were examined in detail for constraining the thermal events using carbon isotope exchange between dolomite/calcite and graphite. Equilibrium carbon isotope fractionation between dolomite and graphite suggested peak metamorphic temperature conditions reaching up to 802°C ± 29°C were estimated at the Balchenfjella locality, where multiple samples from six thick layers of metacarbonate rocks were examined. However, some of the samples exhibit lower carbon isotope fractionation reflecting the possibility of ultrahigh‐temperature metamorphic conditions, which is consistent with recent reports. Furthermore, several metacarbonate rock samples display large variations in δ13CVPDB values for graphite grains, despite dolomite and calcite showing homogeneous carbon and oxygen isotopic composition indicating signatures of retrograde metamorphism and fluid infiltration events. Detailed textural observation suggested alteration of δ13CVPDB values of graphite during retrograde metamorphism might have resulted due to the overgrowth of graphite crystals by the infiltration of low δ13CVPDB‐bearing fluids, the extent of alteration being a direct function of the fluid–rock ratio. Field evidence indicates the presence of carbonate veins cutting across the metacarbonate rocks suggesting that carbon isotope thermometry can also be utilised to understand the effect of external fluid infiltration. At Perlebandet locality the metamorphic temperature conditions were estimated to be around 915°C, whereas those from Tanngarden and Menipa gave lower temperature estimates. Detailed textural analysis of graphite in combination with isotopic composition provided clear evidence for retrograde events. Thus, our results provide tight constraints of peak and post‐peak metamorphic temperature conditions and a regional thermal structure for the Sør Rondane Mountains and further testify the usefulness of carbon isotope thermometry in polymetamorphic terrains.

Interdiffusion Induced Changes in the Absorption Spectra of III-V Quantum Dot Systems

III-V Semiconductor quantum dots (QDs) grown with growth interruption technique do not have uniform group III composition inside the dot. Modelling such as-grown structures requires in-depth knowledge of the composition and potential well profile. In this work, we have developed a three-dimensional analytical model which incorporates strain, as well as the variation of group III composition profile in both lateral and vertical directions inside an as-grown QD in order to quantify the effect of dot size variation on the interband optical absorption spectra of as-grown QD systems. Earlier reports on this subject considered the variation of either the dot height or base to account for the size deviation, which may not be sufficient enough to predict the dot size distribution in realistic systems, where all dimensions are likely to suffer from deviation. Keeping this in mind, Gaussian distribution of dot volume has been adopted here to consider the variations of height and base of QDs in a cumulative way. In our study, we considered InGaAs/GaAs and InGaN/GaN QD systems. The non-uniform distribution of indium inside the as-grown dot leads to a non-rectangular potential well profile, which eventually transforms into a rectangular one after annealing. Through the proposed model, we have investigated the effect of inhomogeneous indium composition and dot size variation on the optical absorption spectra of InGaAs/GaAs and InGaN/GaN as-grown QD systems through Gaussian distribution of dot volume. We have also discussed the effect of size deviation on the full width at half maxima (FWHM) of both as-grown and annealed QD systems. Emphasis has been given to the changes in the conduction and valence band potential profiles due to changes in the morphology inside the dot leading to subsequent changes in the energy levels caused by composition uniformity due to annealing and interdiffusion, thus modifying the nature of absorption spectra.

Force density induced by preferential adsorption in a near-critical binary fluid mixture subject to the Soret effect.

We assume that two parallel plates are immersed in a binary fluid mixture lying in the one-phase region near the demixing critical point and that the surface of each plate attracts the mixture components differently via short-range interactions. It is known that the composition inhomogeneity caused by the difference can induce a force exerted on the plate at equilibrium. In the present study, we investigate how a temperature gradient imposed vertically on the plates changes the induced force by calculating the composition profile subject to the Soret effect. Numerically solving the derived differential equation, we show that a temperature gradient within the critical regime can change the force distinctly from its equilibrium value and can make the force direction opposite to the one at equilibrium.

The chemical and Sm–Nd isotopic behaviour of accessory minerals in metasediments along the LP-HT Chugach Metamorphic Complex (Alaska)

The study of accessory phases, including trace element concentrations and radiogenic isotopes, provides powerful information for a better understanding of geological processes such as crustal anatexis. These accessory minerals are the primary carriers of many incompatible elements and Rare Earth Elements (REE) in crustal rocks. In this contribution, we provide a detailed study on the chemical and isotopic (Nd isotopes) behaviour of accessory minerals within the Chugach Metamorphic Complex in Alaska. This Eocene (55− 50 Ma) metamorphic complex developed in a Late Cretaceous to Paleogene accretionary prism consisting of metapelitic and metagreywacke rocks. The complex exposes a systematic N-S metamorphic gradient from greenschist to upper amphibolite facies (500 to ~ 700 °C) with anatexis under water-saturated conditions and minor muscovite breakdown. Trace element concentration data for apatite, monazite and titanite reveal a strong influence of bulk composition (greywacke vs. pelite) on their REE signatures in the migmatitic gneisses. In xenotime-bearing metapelitic samples, we show that monazite and apatite, which crystallised close to peak metamorphism, have their HREE-Y contents increasing with temperature within a narrow range of ~ 150 °C (550 to ~ 700 °C). While the influence of temperature on the Y content of monazite was already demonstrated before, we prove that apatite follow the same chemical behaviour. In these samples, partial melting process can be tracked via Eu/Eu* which decreases systematically from schist to migmatitic gneisses and is interpreted to be related to plagioclase crystallisation. Among all analysed samples (schists and migmatites), we observe no significant differences in εNd between monazite, allanite and whole-rock, regardless of rock type. This suggests (i) a general homogeneity of Nd isotopic composition above 550 °C up to crustal anatexis, and (ii) an isotopic equilibrium between mineral and whole-rock, indicating Nd isotopic disequilibria induced by partial melting are unlikely in this case study.

Characterisation of Five Natural Magnetite Reference Materials for In Situ Iron Isotope Measurement with Application to Magmatic Ni‐Cu Sulfide Mineralisation

Iron isotope ratios in magnetite have been widely used to reveal critical geological and biological processes. Laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) is ideally suited for measurement of Fe isotope ratios, however the lack of suitable reference materials poses a significant challenge for in situ Fe isotopic measurements in magnetites. In this study, five high‐quality natural magnetite crystals were characterised for Fe isotope ratios using solution nebulisation (SN)‐MC‐ICP‐MS and LA‐MC‐ICP‐MS. The effects of LA‐MC‐ICP‐MS analytical conditions were investigated to obtain precise and accurate Fe isotope ratios. The yielded intermediate measurement precisions for the δ56Fe values in the five investigated magnetites were ± 0.05–0.06‰ (2s) using SN‐MC‐ICP‐MS and ± 0.08–0.14‰ (2s) using LA‐MC‐ICP‐MS. Magnetites with homogeneous Fe isotopic compositions in hand‐specimen measurements and microanalysis can serve as potential reference materials for in situ Fe isotopic measurement. Furthermore, the Fe isotope ratios in the magnetites from the Jinchuan Ni‐Cu‐PGE sulfide deposit were measured using LA‐MC‐ICP‐MS with natural magnetite as the bracketing calibrator. The increase in the Fe isotopic composition with magmatic sulfide evolution was primarily dominated by oxygen fugacity (fO2) and hydrothermal fluids. This finding implies that the Fe isotopic composition of magnetite can serve as a potential geochemical indicator of magmatic Ni‐Cu sulfide mineralisation.

Modulating phase segregation during spin-casting of fullerene-based polymer solar-cell thin films upon minor addition of a high-boiling co-solvent

The impact of additives on the nanoscale structures of spin-cast polymer composite films, particularly in polymer solar cells, is a topic of significant interest. This study focuses on the blend film comprising poly(thieno[3,4-b]thiophene-alt-benzodithiophene) (PTB7) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), exploring how additives like 1,8-diiodooctane (DIO) influence the film structures spin-cast from chlorobenzene solution. Combined results of specular X-ray and neutron reflectivity, grazing-incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS), and X-ray photoelectron spectroscopy indicate that DIO could significantly enhance the dispersion of PC71BM and reduce composition inhomogeneity in the film. Time-resolved GISAXS–GIWAXS with 100 ms resolution further captures a rapid spinodal decomposition of the mixture within 1 s in the constant-evaporation stage of spin-casting. Further combined with parallel analysis of time-resolved UV–Vis reflectance, these findings reveal that DIO mitigates the spinodal decomposition process by accelerating solvent evaporation, which, in turn, decelerates phase segregation, leading to a nucleation-driven process. These observations provide mechanistic insights into the role of additives in controlling the nanostructural evolution of spin-cast films by altering the kinetics of solvent evaporation and phase separation during the spin-coating process.

Wild again: recovery of a beneficial Cannabis seed endophyte from low domestication genotypes

BackgroundBeyond carrying the plant embryo, seeds harbour intricate microbial communities whose transmission across successive plant generations can significantly influence the ecological and evolutionary dynamics of plant–microbe symbioses. The process of plant domestication has potential repercussions in genes involved in plant-microbiome interactions. However, the extent to which breeding can impact the seed microbiome is sparsely explored. Cannabis is a high-value crop but sparsely subjected to agricultural innovations established in other crop species during the last century. Here, we conduct a large-scale analysis of the bacterial seed microbiome of Cannabis across different domestication grades and investigate the potential of seed-associated endophytes as plant growth-promoting agents under both controlled and field conditions.ResultsAnalysis of Cannabis seed endophyte composition and diversity across 46 plant genotypes revealed 813 different bacterial genera with a predominance of Gammaproteobacteria, Bacilli, Actinobacteria and Alphaproteobacteria but a genotype-specific microbiome. The assessment of domestication and breeding on microbial assembly revealed a higher bacterial diversity in low domestication genotypes (Shannon index, H′: 1.21 vs. 1.05) and a higher homogeneity in bacterial composition caused by line development. Further, a seed bacterial isolate (Bacillus frigoritolerans C1141) associated with low domestication genotypes, and with genes associated with bio-fertilization, bioremediation and phytohormone production, increased plant growth by 42.3% at the time of harvest, under field conditions.ConclusionThis study addresses critical knowledge gaps related to the assembly of the Cannabis seed-endophytic microbiome. It reveals that Cannabis breeding is linked to alterations of seed microbial communities, which potentially led to the loss of bacteria with functional significance. These results highlight the importance of preserving seed microbiomes in plant breeding to support sustainable plant health and growth enhancement in Cannabis.CAHvc7HPtw2foEoMit4yw-Video

Soil inoculation changed soil microbial communities, but did not accelerate the decomposition of European Beachgrass (Ammophila arenaria) in Point Reyes National Seashore

Legacy effects after the removal of invasive plants present significant challenges to restoration. The pivotal role of soil microbial communities in shaping these legacy effects is increasingly recognized, yet there is a lack of effective methods to mitigate altered microbial communities. In Point Reyes National Seashore (California), although the invaded European beachgrass (Ammophila arenaria [L.] Link) was successfully controlled by herbicide treatment, beachgrass litter remained undecomposed for over 5 years, leaving pronounced legacy effects on soil organic matter and microbial community composition. We hypothesized that soil inoculation from uninvaded dune scrub can accelerate the decomposition of beachgrass litter in herbicide‐treated sites by restoring the soil microbial communities and the abundance of microbial decomposers. Three litterbags containing European beachgrass litter or litter from two common shrubs at dune scrub were deployed into each plot to assess the impact of soil inoculation on litter decomposition rates. Our results revealed that soil inoculation, regardless of the inoculation level, did not accelerate the decomposition of European beachgrass. Only the decomposition of bush lupine litter, which had the highest litter quality among three types of litter, was accelerated at the highest inoculation level (approximately 11,880 g/m2). Additionally, soil inoculation increased the richness and compositional homogeneity of soil microbial communities, along with the relative abundances of wood saprotrophic fungi, soil saprotrophic fungi, and lichenized fungi. Although these findings demonstrate the potential of soil inoculation, the cost‐effectiveness of soil inoculation limits its feasibility in accelerating the delayed decomposition of European beachgrass litter in Point Reyes.

Ratio optimization and grouting effect of low-viscosity and high-flexibility polymer

A new waterborne epoxy resin (polymer) was studied as a potential grouting material to improve the conventional epoxy resin's high viscosity, brittleness and poor environmental performance. The polymer's formulation was meticulously tailored and optimized by adjusting the curing/hardening time, solid content, viscosity and mechanical properties. Concurrently, grouting tests and scanning electron microscope (SEM) were carried out to scrutinize the diffusion effects and microscopic morphology of three distinct grouted sands, employing polymer, superfine cement and sodium silicates as grouting materials. The results show that the polymer performance is optimal when the polymer ratio is CC-190. CC-190 exhibits a homogeneous composition with 100 % solid content. The initial viscosity of CC-190 stands at a mere 19.2 mPa·s and peak compressive strength of 10.8 MPa. The compression ratio (compression height/original height) and rebound rate (rebound height/original height) of CC-190 remain consistently above 35 % and 93 %, respectively. Grouting tests underscore that polymer outperforms superfine cement and sodium silicates in terms of diffusion distance and grouting volume. Microscopic examination of the grouted sands elucidates that the polymer engenders a sophisticated three-dimensional cross-linked skeletal network, effectively binding and encapsulating individual sand particles. This skeletal framework imparts robust binding forces, ensuring the structural integrity of the grouted sand when subjected to external forces.

Challenges and Prospects of DNA-Encoded Library Data Interpretation.

DNA-encoded library (DEL) technology is a powerful platform for the efficient identification of novel chemical matter in the early drug discovery process enabled by parallel screening of vast libraries of encoded small molecules through affinity selection and deep sequencing. While DEL selections provide rich data sets for computational drug discovery, the underlying technical factors influencing DEL data remain incompletely understood. This review systematically examines the key parameters affecting the chemical information in DEL data and their impact on hit triaging and machine learning integration. The need for rigorous data handling and interpretation is emphasized, with standardized methods being critical for the success of DEL-based approaches. Major challenges include the relationship between sequence counts and binding affinities, frequent hitters, and the influence of factors such as inhomogeneous library composition, DNA damage, and linkers on binding modes. Experimental artifacts, such as those caused by protein immobilization and screening matrix effects, further complicate data interpretation. Recent advancements in using machine learning to denoise DEL data and predict drug candidates are highlighted. This review offers practical guidance on adopting best practices for integrating robust methodologies, comprehensive data analysis, and computational tools to improve the accuracy and efficacy of DEL-driven hit discovery.

Dependence of rheological characteristics of epoxy adhesive binder on the degree of homogeneity of the premix composition

Dependence of rheological characteristics of epoxy adhesive binder on the degree of homogeneity of the premix composition

On the nonmagnetic atom disorder influence in the magnetic and magnetocaloric properties of the Er2Cu0.92Si2.76 off-stoichiometric single-phase compound

This paper presents and discusses material aspects, as well as the magnetic and magnetocaloric properties of nominal Er2Cu0.92Si2.76 alloy synthesized by arc melting. The stoichiometric alloy, prepared with a precise 2(Er):1(Cu):3(Si) ratio, adopts dual symmetries manifesting AlB2-type hexagonal and ThSi2-type tetragonal structures. It was observed that stoichiometric deviations by reducing both Cu/Si concentrations imply a decrease in the tetragonal phase fraction. An 8 % reduction in Cu and Si contents leads to the formation of an off-stoichiometric single-phase: the Er2Cu0.92Si2.76 phase - the focus of this investigation. Notably, Er2Cu0.92Si2.76 showed a uniform grain microstructure without porous and with a homogeneous elemental composition. On the other hand, a long-range antiferromagnetic ordering around 5.6 K was noticed, with a weak influence of magnetic frustration likely arising from nonmagnetic atomic disorder and vacancy at the Cu/Si site. An external magnetic field (greater than 10 kOe) induces ferromagnetic-like ordering, with a saturation tendency at ≈ 50 kOe, corresponding to half the expected magnetic moment for fully ordered Er3+ ions. Er2Cu0.92Si2.76 exhibits large magnetocaloric properties, with isothermal entropy change and relative cooling power values reaching 14.6 J/kgK and 312 J/kg, respectively, for a magnetic field change of 50 kOe. The absence of magnetic and thermal hysteresis is also an attractive prospect for this material aimed at magnetic refrigeration applications at low temperatures.

Improving compositional homogeneity of CF53 steel products by modifying their solidification structure and F-EMS intensity

In this article, based on the mechanism of stirring induced solute washing, the solidification characteristics of CF53 steel for camshafts were systematically studied through industrial casting tests and numerical simulations, focusing on the impact of solidification structure and final electromagnetic stirring (F-EMS) on solute distribution homogeneity in the core area of the bloom casting. The results indicate that excessive columnar crystal development, coupled with inappropriate use of F-EMS, can lead to significant negative segregation in the bloom, resulting in the formation of “white bands” in the following rolling bar products. Compared with weak stirring, strong stirring can affect solutes at deeper levels between dendrites. By reducing superheat and casting speed, expanding the equiaxed crystal zone in the bloom's centre, and carefully controlling the stirring intensity of F-EMS to position the molten steel washing in the equiaxed crystal zone, along with maintaining a maximum tangential velocity of 0.0041 m/s, a substantial improvement in solute distribution homogeneity within the bloom's core area was achieved. The carbon range can be reduced from 0.093% to 0.032%. These findings offer a theoretical foundation and practical suggestions for enhancing the quality of CF53 steel bloom castings and their hot-rolled bar products used in camshaft manufacture.

Synthesis Methods of Si/C Composite Materials for Lithium-Ion Batteries

Silicon anodes present a high theoretical capacity of 4200 mAh/g, positioning them as strong contenders for improving the performance of lithium-ion batteries. Despite their potential, the practical application of Si anodes is constrained by their significant volumetric expansion (up to 400%) during lithiation/delithiation, which leads to mechanical degradation and loss of electrical contact. This issue contributes to poor cycling stability and hinders their commercial viability, and various silicon–carbon composite fabrication methods have been explored to mitigate these challenges. This review covers key techniques, including ball milling, spray drying, pyrolysis, chemical vapor deposition (CVD), and mechanofusion. Each method has unique benefits; ball milling and spray drying are effective for creating homogeneous composites, whereas pyrolysis and CVD offer high-quality coatings that enhance the mechanical stability of silicon anodes. Mechanofusion has been highlighted for its ability to integrate silicon with carbon materials, showing the potential for further optimization. In light of these advancements, future research should focus on refining these techniques to enhance the stability and performance of Si-based anodes. The optimization of the compounding process has the potential to enhance the performance of silicon anodes by addressing the significant volume change and low conductivity, while simultaneously addressing cost-related concerns.

Synthesis of group-IV ternary and binary semiconductors using epitaxy of GeH3Cl and SnH4

Ge1−x−ySixSny alloys were grown on Ge buffers via reactions of SnH4 and GeH3Cl. The latter is a new CVD source designed for epitaxial development of group-IV semiconductors under low thermal budgets and CMOS-compatible conditions. The Ge1−x−ySixSny films were produced at very low temperatures between 160 and 200 °C with 3%–5% Si and ∼5%–11% Sn. The films were characterized using an array of structural probes that include Rutherford backscattering, x-ray photoelectron spectroscopy, high-resolution x-ray diffraction, scanning transmission electron microscopy, and atomic force microscopy. These studies indicate that the films are strained to Ge and exhibit defect-free microstructures, flat surfaces, homogeneous compositions, and sharp interfaces. Raman was used to determine the compositional dependence of the vibrational modes indicating atomic distributions indistinguishable from those obtained when using high-order Ge hydrides. For a better understanding of the growth mechanisms, a parallel study was conducted to investigate the GeH3Cl applicability for synthesis of binary Ge1−ySny films. These grew strained to Ge, but with reduced Sn compositions and lower thicknesses relative to Ge1−x−ySixSny. Bypassing the Ge buffers led to Ge1−ySny-on-Si films with compositions and thicknesses comparable to Ge1−ySny-on-Ge; but their strains were mostly relaxed. Efforts to increase the concentration and thickness of Ge1−ySny-on-Si resulted in multiphase materials containing large amounts of interstitial Sn. These outcomes suggest that the incorporation of even small Si amounts in Ge1−x−ySixSny might compensate for the large Ge–Sn mismatch by lowering bond strains. Such an effect reduces strain energy, enhances stability, promotes higher Sn incorporation, and increases critical thickness.

Thermally-induced diffusion and structural phase transitions in Pt/Mn and Pt/Mn/Pt thin films

We demonstrate the possibility of diffusion formation of the chemically ordered L1 0-MnPt phase through the vacuum annealing of Pt(24 nm)/Mn(20 nm) and Pt(12 nm)/Mn(20 nm)/Pt(12 nm) layered stacks at 400 °C for 30 min. For the bi-layered stack annealed at 400 °C, the effect of Pt atoms segregation at the film/substrate interface was detected, which remained after annealing even at higher temperatures (500 °C and 600 °C) and prevented the whole homogenization of the chemical composition through the film depth. By contrast, for the tri-layered stack annealed at 400 °C, the presence of the additional Pt bottom layer enabled to change the rate and mechanism of reactive diffusion, leading to homogeneous distribution of components and enhanced crystallinity of the ordered L1 0-MnPt phase compared to the bi-layered sample. An explanation of the obtained experimental data is provided based on the fundamentals of mass transfer theory and its quantitative parameters (e.g. activation energy and diffusion coefficients).

Effect of Horizontal Continuous Casting Parameters on Cyclic Macrosegregation, Microstructure, and Properties of High-Strength Cu–Mg Alloy Cast Rod

AbstractThe objective of this paper is to present the effect of horizontal continuous casting parameters on macrosegregation and its effect on microstructures, textures, mechanical properties, and electrical resistivity of Cu–Mg alloy rod. By increasing the pulling distance and intermittent extraction time, chemical macrosegregation was observed along the longitudinal section of the cast rod, which reached a distance of 40 mm. Three areas were identified along the length of the material, especially at high pulling distance: with decreasing, quasi-stable, and increasing Mg concentration area. As the pulling distance increased, the difference in the observed extreme values of Mg concentration increased. Two distinct zones of different grain size were also observed. The first zone was formed of large columnar grains with a preferred direction of solidification $$\langle 100\rangle$$ ⟨ 100 ⟩ inclined to the axis of the wire, followed by a second zone formed of small grains of random texture. Consequently, difference in resistivity occurred from one zone to another and the resistivity increased from 37.5 to 41 nΩm. Likewise, the hardness varied between the values of 90 up and 110 Hv. The most homogenous chemical composition was obtained with up to 6 mm of pulling distance and up to 3 seconds of intermittent extraction time.