Solids

15 pages, 4143 KB

Open AccessArticle

Microstructure and Mechanical Performance of Cu and Gr/Cu Composites: Experimental and Ab Initio Insights

by Galiia Korznikova, Gulnara Khalikova, Igor Kosarev, Wei Wei, Alexander Semenov and Elena Korznikova

Solids 2025, 6(4), 57; https://doi.org/10.3390/solids6040057 - 8 Oct 2025

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Abstract

This study investigates the microstructure and mechanical properties of copper (Cu) and graphene/Cu (Gr/Cu) composites produced via high-pressure torsion (HPT) under 5 GPa at room temperature. Microstructural analysis revealed significant grain refinement, with average grain sizes of 0.39 μm for pure Cu and 0.35 μm for Gr/Cu composite. The Gr/Cu composite exhibited slightly higher microstrains and effective stacking fault energy (SFE). Tensile tests showed ultimate tensile strengths of 689 MPa (pure Cu) and 674 MPa (Gr/Cu), with the latter demonstrating improved ductility (~10% elongation). Ab initio calculations confirmed a 27% increase in SFE for Gr/Cu, aligning with experimental results. These findings highlight the potential of Gr/Cu composites for applications requiring high strength and efficient heat dissipation. Full article

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22 pages, 5267 KB

Open AccessArticle

On Ballooning and Burst Behavior of Nuclear Fuel Clad Considering Heating Rate Effect: Development of a Damage Model, a Burst Correlation and Experimental Validation

by Ather Syed and Mahendra Kumar Samal

Solids 2025, 6(4), 56; https://doi.org/10.3390/solids6040056 - 28 Sep 2025

Viewed by 315

Abstract

Nuclear fuel cladding serves as the primary barrier to the release of radioactive fission products and is subjected to high-temperature and high-pressure environments during both normal reactor operation and accident scenarios such as loss of coolant accidents (LOCAs). Predicting the burst behavior of cladding is essential for ensuring structural integrity, especially under varying heating rates—an aspect inadequately addressed in existing empirical models. In this study, a finite element-based damage model is developed to simulate the ballooning and burst behavior of Zircaloy-4 cladding. The model incorporates creep deformation, stress triaxiality, and time-dependent damage accumulation. Material behavior is characterized using experimentally determined creep constants and the model is calibrated against burst test data from the literature. A new heating-rate-dependent burst correlation is proposed based on model outputs. The results indicate that increasing the heating rate raises the burst temperature due to reduced exposure time in the temperature regime where creep damage accumulates significantly. The model accurately reproduces burst behavior across a wide range of internal pressures (1–10 MPa) and heating rates (5–100 °C/s). The newly developed correlation improves predictive capability in accident analysis tools and can be directly implemented into safety analysis codes for Indian pressurized heavy water reactors (PHWRs), contributing to enhanced reactor safety evaluations. Full article

(This article belongs to the Topic Multi-scale Modeling and Optimisation of Materials)

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19 pages, 6620 KB

Open AccessArticle

DFT Study of Oxygen Ion Migration in Mg-Doped Cubic Zirconia

by Zhussupbek M. Salikhodzha, Guldari B. Bairbayeva, Anatoli I. Popov, Raigul N. Kassymkhanova, Keleshek B. Zhangylyssov, Elena Popova and Marina Konuhova

Solids 2025, 6(4), 55; https://doi.org/10.3390/solids6040055 - 25 Sep 2025

Viewed by 410

Abstract

This work presents a theoretical investigation of ionic conductivity in cubic zirconia (c-ZrO₂) doped with magnesium, using density functional theory (DFT) with the hybrid B3LYP functional as implemented in the CRYSTAL23 software package. It was found that the spatial arrangement of magnesium atoms and oxygen vacancies significantly affects the energy barriers for oxygen ion migration. Configurations with magnesium located along and outside the migration path were analyzed. The results show that when Mg²⁺ is positioned along the migration trajectory and near an oxygen vacancy, stable defect complexes are formed with minimal migration barriers ranging from 0.96 to 1.32 eV. An increased number of Mg atoms can lead to a further reduction in the barrier, although in certain configurations the barriers increase up to 3.0–4.6 eV. When doping occurs outside the migration path, the energy profile remains symmetric and moderate (0.9–1.1 eV), indicating only a weak background influence. These findings highlight the critical role of coordinated distribution of Mg atoms and oxygen vacancies along the migration pathway in forming efficient ion-conducting channels. This insight offers potential for designing high-performance zirconia-based electrolytes for solid oxide fuel cells and sensor applications. Full article

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Solids, Volume 6, Issue 4 (December 2025) – 3 articles

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