NaA zeolite was synthesized using sodium silicate and sodium aluminate precursors via the reflux method at 80 degrees C with time variations of 1, 3, and 5 h, producing samples Z801H, Z803H, and Z805H. The influence of reflux time on the physicochemical properties and catalytic activity of the zeolites was systematically investigated. XRD and FTIR analyses confirmed a progressive transformation from amorphous aluminosilicate (1 h) to partially crystalline zeolite (3 h), and to highly crystalline NaA zeolite (5 h), with a consistent Si/Al ratio of 1.0 as determined by EDX. SEM micrographs revealed morphological evolution from amorphous gel to well-defined cubic NaA crystals. BET analysis showed that Z801H and Z803H were mesoporous with higher surface area (46.49 and 28.26 m2/g) and pore volume, while Z805H was microporous with very low surface area (1.28 m2/g). Acidity, measured by NH3 adsorption, followed the same trend, with Z801H exhibiting the highest acidity (1.22 mmol/g). Catalytic activity was tested in the esterification of acetic acid with butanol. The use of zeolite catalysts significantly enhanced ester yield compared to the non-catalyzed reaction (34.81%), with Z801H achieving the highest yield (75.95%). GC-MS confirmed butyl acetate as the main product. These results demonstrate that reflux time strongly governs zeolite structure, porosity, and catalytic performance.
Developing hydrogen-resistant materials is still a central challenge for the hydrogen economy. This study investigates whether additively manufactured stainless steel exhibit enhanced resistance to hydrogen embrittlement (HE) relative to their conventionally processed variant. Samples produced using Powder Bed Fusion-Laser Beam/Metal (PBF-LB/M) were manufactured to analyze their microstructure, hydrogen trapping, and permeability. Electrochemical measurements showed that the permeation currents follow an exponential dependence, consistent with Fick's law of diffusion. The apparent diffusion coefficients and breakthrough times varied depending on the conditions during laser processing. X-ray absorption spectroscopic data confirmed these results, indicating higher distortions in the face-centered cubic structure of the steel and an increased number of hydrogen traps at optimized parameters. Our results show that targeted control of additive manufacturing parameters strongly determines, i.e., improves or worsens, the resistance to HE.
Two-dimensional nanomaterials have attracted extensive attention owing to their unique lamellar structures and physicochemical properties. Branched structure endows two-dimensional nanomaterials with more active sites and excellent catalytic and sensing performances. However, the preparation of dendritic lamellar nanomaterials that integrate both two-dimensional lamellar architecture and branched structure remains a great challenge. Here, we prepared two-dimensional dendritic gold nanosheets (DGNs) via the emulsion-mediated strategy using the triblock copolymer F127 (PEO100-PPO65-PEO100). The SEM results show that DGNs have a two-dimensional lamellar branched structure. The particle size and lamellar thickness of DGNs are 5340 nm and 90 nm, respectively. The lengths of the primary, secondary, and tertiary branches of DGNs are 2480, 1410, and 650 nm, respectively. Furthermore, three-dimensional lamellar flower-like structures and rod-like branched structures are obtained by adjusting the concentration of TMP (2,3,6-trimethylphenol). This novel emulsion-mediated method paves the way for the preparation of two-dimensional nanomaterials with branched structures.
