Abstract Deep neural network (DNN) exhibits state-of-the-art performance in many fields including microstructure recognition where big dataset is used in training. However, DNN trained by conventional methods with small datasets commonly shows worse performance than traditional machine learning methods, e.g. shallow neural network and support vector machine. This inherent limitation prevented the wide adoption of DNN in material study because collecting and assembling big dataset in material science is a challenge. In this study, we attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points. It is found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods. The trained DNN transforms scattered experimental data points into a map of high accuracy in high-dimensional chemistry and processing parameters space. Though DNN with big datasets is the optimal solution, DNN with small datasets and pre-training can be a reasonable choice when big datasets are unavailable in material study.
Gradient structures are characterized with a systematic change in microstructures on a macroscopic scale. Here, we report that gradient structures in engineering materials such as metals produce an intrinsic synergetic strengthening, which is much higher than the sum of separate gradient layers. This is caused by macroscopic stress gradient and the bi-axial stress generated by mechanical incompatibility between different layers. This represents a new mechanism for strengthening that exploits the principles of both mechanics and materials science. It may provide for a novel strategy for designing material structures with superior properties.
Nations using borosilicate glass as an immobilization material for radioactive waste have reinforced the importance of scientific collaboration to obtain a consensus on the mechanisms controlling the long-term dissolution rate of glass. This goal is deemed to be crucial for the development of reliable performance assessment models for geological disposal. The collaborating laboratories all conduct fundamental and/or applied research using modern materials science techniques. This paper briefly reviews the radioactive waste vitrification programs of the six participant nations and summarizes the current state of glass corrosion science, emphasizing the common scientific needs and justifications for on-going initiatives.
ObjectiveTo explore the effects of the dosage and application time of MH saline-alkali land improvement materials prepared from pulverized coal furnace fly ash on the physical and chemical properties of saline-alkali soil, MethodMH saline-alkali land improvement material prepared with fly ash produced by the pulverized coal furnace process as the base material was subjected to a 25-day soil pot experiment indoors. ResultWith different application rates of MH saline-alkali land improvement materials, the pH value, HCO3-, and exchangeable sodium ion content of the saline-alkali soil all showed a gradually decreasing change pattern over time. When the application rate was 2.5% and the saline-alkali soil was cultivated indoors for 25 days, the soil pH value decreased by 0.64 units and HCO3- decreased by 57.16%. The content of exchangeable sodium ions decreased by 77.27%. Phosphorus and fast-acting potassium content were increased to different degrees, soil bulk weight was reduced to 1.40 g/cm3, porosity was increased by 6.83%, and the proportional distribution of soil solid, liquid and gas was significantly modified. However, organic matter and cation exchange were reduced by 46.06% and 29.96%, respectively, compared with the test soil. ConclusionMH saline improvement materials can effectively regulate the physical and chemical properties of saline soil and improve the crop growth environment.
Orest Pavlosiuk, Marcin Matusiak, Andrzej Ptok
et al.
Topologically trivial and non-trivial semimetals with a high degree of carrier compensation are well known for demonstrating large transverse magnetothermopower ($S_{yx}$). However, in such systems, the longitudinal magnetothermopower ($S_{xx}$) is typically suppressed due to nearly perfect electron-hole compensation. Here, we show that the half-Heusler topological semimetal DyPtBi exhibits simultaneously large $S_{xx}$ and $S_{yx}$ magnetothermopowers, defying this conventional trade-off. In $B=14$\,T, thermopower of DyPtBi reaches peak values of $S_{xx}=131\,μ\rm{V/K}$ at $T=149$\,K and $S_{yx}=-297\,μ\rm{V/K}$ at $T=200$\,K, and transverse component remains significantly large even at $290$\,K ($S_{yx}=-213\,μ\rm{V/K}$). Remarkably, at $T=290$\,K and in relatively weak magnetic field of $1$\,T, both relevant for practical applications, DyPtBi shows $S_{yx}=-18\,μ\rm{V/K}$, which is one of the largest values reported under such conditions. The large transverse thermopower originates from an ambipolar effect associated with thermal excitation occurring in zero-gap semiconductors. Due to the imperfect electron-hole compensation, an intrinsic asymmetry between hole- and electron-type carriers enables pronounced values of both $S_{xx}$ and $S_{yx}$, resulting in high effective thermopower ($S_{xx}+|S_{yx}|=379\,μ\rm{V/K}$) in DyPtBi at 200\,K. A comparative analysis with DyPdBi, another half-Heusler material that demonstrates large $S_{xx}=123\,μ\rm{V/K}$ but small $S_{yx}=-16\,μ\rm{V/K}$ (both values obtained at $T=293$\,K and $B=14$\,T), highlights the critical role of band structure and compensation tuning. These findings underscore the potential of chemical doping and band engineering in rare-earth-based half-Heusler materials for optimizing both transverse and longitudinal thermoelectric properties.
Detection Dmitry N. Dirin,†,‡ Ihor Cherniukh,†,‡ Sergii Yakunin,†,‡ Yevhen Shynkarenko,†,‡,§ and Maksym V. Kovalenko*,†,‡ †Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland ‡Laboratory for Thin Films and Photovoltaics, Empa − Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland Department of Photonic Processes, Institute of Physics, National Academy of Sciences of Ukraine, 46 Prospekt Nauky, Kyiv 03680, Ukraine
With the increasingly demanding service conditions of coiled tubing, its welded joints require superior synergistic strength-toughness properties to meet comprehensive mechanical performance requirements. This study achieved synergistic optimization of strength and toughness in deposited metal via lanthanum microalloying technology and elucidated microstructural evolution mechanisms and fracture failure mechanisms via multi-scale characterization techniques. The results demonstrate that lanthanum oxide addition effectively modifies inclusion characteristics, inducing phase transformation from O-Mn-Si-Al-Ti to O-Mn-Si-Al-Ti-S-La, with average particle size significantly decreased from 0.19 μm to 0.12 μm. The deposited metal microstructure comprises lath bainite and granular bainite. The addition of 0.5 wt.% lanthanum oxide results in significant microstructural refinement: average grain size decreases from 1.16 ± 1.18 μm to 1.02 ± 1.00 μm, while granular bainite volume fraction decreases from 8.6% to 4.7%. The microstructural optimization also enhances mechanical properties substantially: yield strength increases from 628 ± 14 MPa to 673 ± 12 MPa, and impact toughness improves from 160 ± 6 J to 189 ± 6 J. Mechanistic analysis revealed that proper addition of lanthanum (0.5 wt.%) promotes grain refinement via heterogeneous nucleation and modifies inclusion morphology, effectively inhibiting crack initiation. However, excessive addition (1.0 wt.%) induces inclusion clustering, forming stress concentration sites that degrade mechanical properties.
Puput Risdanareni, Vita Ayu Kusuma Dewi, Ruri Agung Wahyuono
et al.
Hydrogel-based self-healing mortar often experiences strength decrease that may impact concrete performance under mechanical load. While the addition of commercial colloidal nano silica can improve the strength of hydrogel-based self-healing mortar, they can be relatively expensive. This work examines the synthesis of an alternative and affordable nano-silica, aiming to improve the mechanical strength of hydrogel-based self-healing mortar. Nano silica is extracted from abundantly available mineral admixture, i.e., fly ash through chemical purification methods. Two concentrations of 2 % and 5 % nano silica by mass replacement of cement are used in the mortar mixture. X-ray diffraction was conducted to ensure that nano silica produced is in amorphous form. The hydration kinetics of resulting paste, workability, compressive strength, healing capacity and capillary water absorption of resulting mortar were investigated. The results prove the production of high-quality nano silica from fly ash with sufficient amorphous phase. The hydration kinetics indicate that the incorporation of nano-silica derived from fly ash at a dosage of 2 % accelerates the hydration reaction. This acceleration corresponds with the observed enhancement in the compressive strength of hydrogel-loaded mortar, where the addition of 2 % nano-silica fly ash produced strength values comparable to those of the reference sample while maintaining the self-healing capability. Therefore, a dosage of 2 % nano-silica fly ash by cement weight is recommended as an effective mineral additive for improving the mechanical performance of hydrogel-based self-healing mortars.
Materials of engineering and construction. Mechanics of materials
A comparative study is presented on the dependence of optical and material properties of VCSELs on Ge and GaAs substrate thicknesses as well as epitaxy process conditions. It was found that adjusting the Ge substrate thickness and optimizing the epitaxy process can shift the stopband center and cavity resonance wavelength by several nanometers. Ge-based VCSELs exhibit improved epitaxial uniformity, smaller deviations from design specifications, reduced stoichiometry variations, and strain magnitudes comparable to those of GaAs-based counterparts. In the selected 46.92 μm<sup>2</sup> sample area, no defects were observed in the quantum well (QW) regions of Ge-based VCSELs, and the threading dislocation density (TDD) was measured to be below 2.13 × 10<sup>6</sup> cm<sup>−2</sup>. These results highlight the potential of Ge substrates as promising candidates for advanced VCSELs.
The surface morphology of lithium metal electrodes evolves markedly during cycling, modulating interfacial kinetics and increasing the risk of dendrite-driven internal short circuits. Here, we infer this morphological evolution from direct-current (DC) signals by analyzing open-circuit voltage (OCV) transients after constant current interruptions. The OCV exhibits a rapid initial decay followed by a transition to a slower long-time decay. With repeated plating, this transition shifts to earlier times, thereby increasing the contribution of long-term relaxation. We quantitatively analyze this behavior using an equivalent circuit with a transmission-line model (TLM) representing the electrolyte-accessible interfacial region of the electrode, discretized into ten depth-direction segments. Tracking segment-wise changes in resistances and capacitances with cycling enables morphology estimation. Repeated plating strongly increases the double-layer area near the current collector, while the charge-transfer-active surface shifts toward the separator side, showing progressively smaller and eventually negative changes toward the current-collector side. Together with the segment-resolved time constants, these trends indicate that lithium deposition becomes increasingly localized near the separator-facing surface, while the interior becomes more tortuous, consistent with post-mortem observations. Overall, the results demonstrate that DC voltage-relaxation analysis combined with a TLM framework provides a practical route to track lithium metal electrode surface evolution in Li-metal-based cells.