Synthesis and Sintering

Effect of the K2O/(CaO+ZnO) ratio on crystallization behavior, phase formation, and mechanical properties of transparent borosilicate glazes

Razie Salami — 2026-06-27

The crystallization behavior of transparent borosilicate glass–ceramic glazes is strongly influenced by their chemical composition, particularly the ratio of network modifiers. In this study, the effect of the K2O/(CaO+ZnO) ratio (S ratio) on the phase evolution, microstructure, optical properties, and mechanical performance of transparent borosilicate glazes was investigated. Glazes with different S ratios were prepared under identical processing conditions and characterized by differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), optical measurements, and Vickers microhardness testing. The results showed that decreasing the S ratio significantly affected the thermal stability and crystallization behavior of the glass network. XRD and SEM analyses revealed the formation of wollastonite, willemite, calcium silicate, and calcium aluminosilicate (anorthite) phases, accompanied by distinct changes in crystal morphology. These phase transformations directly influenced the optical appearance and mechanical properties of the glazes. The highest microhardness was obtained for the glaze containing calcium aluminosilicate as the dominant crystalline phase, whereas glazes with a higher residual amorphous content exhibited lower hardness values. Variations in the crystalline phase assemblage also affected the surface gloss and opacity of the fired glazes. Overall, the results demonstrate that the K2O/(CaO+ZnO) ratio is an effective compositional parameter for controlling the crystallization behavior and optimizing the functional properties of transparent borosilicate glass–ceramic glazes.

Crystallinity control in covalent triazine frameworks: Synthetic approaches and mechanistic insights

Asieh Akhoondi — 2026-06-27

An important class of emerging porous organic materials is covalent triazine frameworks (CTFs), which have attracted much attention in wastewater treatment, energy conversion, and gas absorption due to their chemical and thermal properties and high nitrogen content. The synthesis of CTFs faces several challenges, including the reversibility of the reactions, which leads to structural defects and poor crystallinity. As a result, achieving high crystallinity is a major goal in the research and development of CTFs. This brief review focuses on the latest advances in the synthesis and control of crystallinity of these nitrogen-rich materials. The paper proceeds in order to review the principles governing crystal formation, the synthesis methods and factors affecting the reactions, and the final operations to prepare the product to enhance crystallinity. In addition, common crystallinity assessment techniques, including powder X-ray diffraction and advanced analysis, are reviewed. The effect of framework crystal structure on performance optimization is also discussed. Finally, challenges and future prospects in the development of synthesis techniques for the technological advancement of CTFs are presented.

Design and finite element analysis of a bio-inspired cellular airfoil for selective laser melting

Ata Khabaz-Aghdam — 2026-06-27

The demand for lightweight and adaptive aerospace structures has accelerated the development of bio-inspired cellular architectures that combine high structural efficiency with manufacturability through advanced additive manufacturing technologies. In this study, a bio-inspired cellular airfoil intended for fabrication by Selective Laser Melting (SLM) is proposed and its mechanical behavior is investigated through a comprehensive finite element analysis. The cellular architecture was generated using a parametric design methodology inspired by natural internal structural patterns and integrated into two representative NACA airfoils, namely NACA 0010 and NACA 2412. Eighteen design configurations were created by systematically varying the geometric parameters governing the size and position of the internal cellular network. The geometries were generated using MATLAB, verified numerically, and analyzed under static loading conditions using ABAQUS. The distributions of von Mises stress, displacement, structural stiffness, and deformation characteristics were evaluated to identify the influence of geometric parameters on the mechanical response of the airfoils. The results demonstrate that the proposed bio-inspired cellular architecture provides a favorable balance between structural rigidity and deformation capability while significantly reducing the material required within the airfoil. Furthermore, the study identifies optimal geometric configurations that exhibit improved load-carrying capability with relatively uniform stress distributions, making them attractive candidates for lightweight aerospace structures. The proposed design is particularly suitable for fabrication by Selective Laser Melting, which enables the realization of complex enclosed cellular architectures that are difficult or impossible to manufacture using conventional methods. The findings provide useful design guidelines for the development of additively manufactured bio-inspired airfoils and other lightweight aerospace components.

Microstructural transformation and recovery of rare earth elements during hydrochloric acid leaching of apatite concentrate

Erfan Mohammadzadeh — 2026-06-27

Hydrochloric acid concentration plays a pivotal role in governing the dissolution behavior of apatite and the recovery of rare earth elements (REEs) during hydrometallurgical processing. In this study, the influence of hydrochloric acid concentration on the leaching of cerium (Ce), lanthanum (La), and neodymium (Nd) from an apatite concentrate derived from iron ore processing waste was comprehensively investigated by correlating microstructural evolution with leaching performance. The effects of acid concentration, solid-to-liquid (S/L) ratio, leaching time, and temperature were systematically evaluated using Response Surface Methodology (RSM). Statistical analysis identified acid concentration as the most significant parameter controlling REE extraction, followed by leaching temperature, whereas leaching time exhibited only a marginal influence. Under the optimum conditions of 37 wt.% HCl, a solid-to-liquid ratio of 1:9, a leaching time of 60 min, and a temperature of 65 °C, the recoveries of Ce, La, and Nd reached 94.19%, 86.33%, and 76.34%, respectively. SEM analysis of the leaching residues revealed a progressive transition from relatively smooth, well-preserved crystalline particles at low acid concentrations to severely corroded, fragmented, and porous structures at higher acid concentrations. These microstructural transformations provide direct evidence of enhanced apatite decomposition and increased REE liberation, explaining the substantial improvement in extraction efficiency. The strong correlation between acid-induced microstructural evolution and REE recovery demonstrates that hydrochloric acid concentration is the primary driving force governing leaching performance. This study provides new mechanistic insight into acid-assisted apatite dissolution and establishes an optimized, economically attractive strategy for the efficient recovery of valuable REEs from apatite-rich iron ore tailings.