Fusion kinetics and thermomechanical behavior of Ni–Pd core–shell nanoparticles: insights from molecular dynamics simulations

Chemical and Structural Segregation in Ternary Pt–Pd–Cu Nanoparticles: Molecular Dynamics Simulation

Formation mechanism of core–shell structures in Mg-doped BaTiO 3 -based ceramics for high-temperature MLCCs application

Enhancing the thermal stability of dielectric ceramics is crucial for maintaining the reliability of multilayer ceramic capacitors (MLCCs) under fluctuating thermal environments. While core–shell structuring has proven effective in mitigating temperature-dependent permittivity variations, the role of dopant chemistry in governing its formation and associated dielectric stability remains insufficiently understood. In this study, 0.9BaTiO 3 –0.1(Bi 0.5 Na 0.5 )TiO 3 ceramics co-modified with 2.0 mol% Nb 2 O 5 were fabricated via a conventional solid-state method, and different amounts of MgO or MgCO 3 were introduced to systematically investigate the effects of dopant chemistry and incorporation behavior on the microstructure and dielectric properties. Comparative structural analysis revealed that MgO and MgCO 3 exhibited significantly different influence on core–shell structure evolution. MgO, due to its high reactivity and rapid diffusion during sintering, facilitated compositional homogenization and impeded the formation of distinct core–shell structures, thereby leading to a deteriorated temperature coefficient of capacitance (TCC). In contrast, MgCO 3 decomposed progressively during sintering, allowing for delayed and controlled incorporation of Mg 2+ ions, which promotes the development of well-defined core–shell architectures and preserves compositional gradients within grains. As a result, only the MgCO 3 -doped ceramics satisfied the X9R specification, exhibiting excellent dielectric thermal stability over the temperature range of −55 to 200 °C. These results highlight the importance of dopant chemistry and diffusion behavior in controlling core–shell structures and enhancing the thermal stability of lead-free ceramics for high-temperature MLCCs applications.

A molecular dynamics simulation on mechanical and thermodynamic properties of MVIII-metals (Ni, Pd, Pt)/6,6,12-graphyne composite nanostructures

Local Strain in Pt–Ni Bulk and Nanoparticles

Understanding the mechanical behavior of bimetallic nanoparticles under compressive stress is relevant for the use of these nanostructures in catalysis and nanomechanics. In this work, we present molecular dynamics (MD) simulations of compressive deformation in Pt–Ni nanoparticles—and bulk systems for comparison—with varying compositions (PtxNi1−x) and local distributions. The simulations show that the mechanical response is governed by local strain fields, which influence both elastic and plastic regimes. The final trajectories were analyzed by dislocation analysis (DXA), simulated STEM imaging, and geometric phase analysis (GPA), which allowed the obtention of high-resolution strain maps. Analysis of von Mises stress distribution allowed us to correlate composition and atomic ordering with the formation and evolution of dislocations in the nanoparticles. The Pt0.5Ni0.5 intermetallic compound exhibits superior mechanical performance under uniaxial compression; in bulk, this composition also shows enhanced elastic energy storage. In polycrystalline nanoparticles, energy dissipation increased with decreasing average grain size, which is attributed to elevated plastic activity induced by the presence of multiple crystallographic orientations. GPA results show that it is possible to discriminate between compositions differing by as little as Δx = 0.1 based on local strain distributions, and the comparison with GPA performed on real STEM micrographs gives a fair agreement. GPA and atomistic stress maps reveal how strain fields evolve during compression and how they correlate with the development of plasticity. These findings highlight the critical role of local structural heterogeneities in dictating the mechanical behavior of nanoscale Pt–Ni systems, and provide strong evidence that GPA can correlate local strain and composition in real high-resolution micrographs.

From Molecular Structure to Macroscopic Performance: Insights into Polycarbosilane Curing

Curing protocols critically influence the structure and properties of crosslinked polymer networks, yet their impact on nanoscale structural features remains poorly understood. Here, polycarbosilane (PCS) networks are used as a model system to investigate curing‐induced structural evolution across multiple techniques. PCS networks were prepared via Pt‐catalyzed hydrosilylation reaction at progressively higher curing temperatures, and their macroscopic properties were correlated with molecular‐level changes using a combined experimental‐computational approach. Mechanical testing revealed a transition from flexible to brittle behavior with increasing curing temperature, while dynamic mechanical thermal analysis (DMTA) and swelling experiments showed a continuous increase in glass transition temperature (Tg) and crosslink density. Positron annihilation lifetime spectroscopy (PALS) provided direct insight into network development and revealed a redistribution toward larger free‐volume populations despite the higher crosslink density. Molecular dynamics (MD) simulations qualitatively supported this trend by demonstrating reduced segmental mobility and the formation of fewer but larger geometric free volume domains at high conversion, thereby explaining both the increase in free volume and the onset of brittleness. This integrated approach highlights the strong influence of curing temperature on both network architecture and macroscopic performance. Beyond PCS, the methodology provides a generalizable framework for analyzing structure‐process‐property relationships in highly crosslinked polymer networks.

Sol–Gel Engineering of Nanostructured MgFe2O4 Ferrite: Tunable Microstructure for Thermochemical Energy Conversion Applications

This study investigates the synthesis–structure relationships governing sol–gel-derived nanostructured MgFe2O4 ferrite powders for high-temperature thermochemical energy conversion applications. The effects of key processing parameters, including propylene oxide (PO) concentration, gel aging time, calcination temperature, and calcination duration, were systematically examined to tune the phase composition, specific surface area (SSA), pore volume, crystallite size, and nanoparticle morphology of MgFe2O4. Increasing the PO concentration from 5 to 20 mL shortened the gelation time from 585 to 323 s and increased the SSA from 5.30 to 17.88 m2/g, while the pore volume increased from 0.0074 to 0.0210 cm3/g. In contrast, gel aging time between 24 and 120 h produced negligible changes in SSA, pore volume, and crystallite size, indicating that extended aging is not required for microstructural control. Calcination temperature strongly influenced the nanostructure: increasing the temperature from 600 to 1000 °C decreased SSA and pore volume while increasing crystallite size from 21.33 to 48.76 nm. Longer calcination times produced a similar but less pronounced effect, decreasing SSA from 18.83 to 14.89 m2/g and increasing crystallite size from 17.55 to 30.12 nm. Overall, phase-pure MgFe2O4 with favorable textural properties was obtained using 20 mL of PO, 24 h of aging, and calcination in the 700–800 °C range. Under the identified synthesis conditions, namely 20 mL of PO, 24 h of aging, and calcination in the range of 700–800 °C for 2 h, phase-pure MgFe2O4 nanoparticles with particle sizes of approximately 10–50 nm were obtained. These results establish a processing–microstructure framework for engineering MgFe2O4 nanomaterials with tunable textural properties for solar thermochemical redox cycles and related high-temperature energy applications.