Current Science International

Hydrogen Adsorption on Manganese-Doped Carbon, Boron Nitride, and Silicon Carbide Nanocones: A Density Functional Theory Study

2026-03-10

The quest for efficient hydrogen storage media persists as a pivotal bottleneck in the transition toward large-scale hydrogen-based energy infrastructures. In the present study, systematic density functional theory (DFT) calculations were executed via the Gaussian 09 software package to scrutinize the hydrogen adsorption phenomena on pristine and manganese-doped nanocones (NCs) comprising
carbon (C), boron nitride (BN), and silicon carbide (SiC). By employing a rigorous computational framework, we evaluated the structural stability and electronic modulation of these nanostructures to determine their viability for storage applications. Our findings underscore the superiority of the Mn– Si41C34H9–M2 configuration characterized by a 300° disclination angle which demonstrated an
exceptionally robust interaction with molecular hydrogen. This specific system yielded a significant adsorption energy of -4.98 eV, accompanied by a pronounced dipole moment enhancement of 25.74 D, thereby indicating substantial surface polarization. Furthermore, the electronic landscape analysis revealed an ultra-narrow energy gap of 0.02 eV for the Mn-doped SiC nanocone, suggesting a highly reactive state that facilitates charge transfer processes. Natural Population Analysis (NPA) and molecular orbital insights indicate that Mn incorporation induces a localized electronic redistribution, creating potent catalytic sites for hydrogen binding. Comparative assessment confirms that Mn-doped SiC nanocones outperform their C and BN counterparts in terms of binding affinity, highlighting the indispensable role of transition-metal doping in fine-tuning the chemisorption characteristics. These results provide critical theoretical benchmarks for designing dopant-induced nanoscale platforms tailored for high-capacity hydrogen storage.

Optimization of Different Extraction Methods of irradiated Chamomile on Antioxidant Activity and Chamazulene Content Using Response Surface Methodology

2026-03-20

This study successfully determined the optimal supercritical fluid (CO2) extraction (SFE) parameters for recovering high-potency antioxidants from irradiated chamomile (Matricaria recutita L.). Utilizing a Box–Behnken response surface design, the effects of pressure, temperature, and extraction time were modeled to maximize radical-scavenging activity. Determinations of antioxidant activities of chamomile oil samples were accomplished using 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2´- azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods The optimization identified distinct coordinates for peak performance: 257.17 bar, 50°C, and 180 min for DPPH (IC50 = 162.15 μg/mL), and 272.72 bar, 50°C, and 131.51 min for ABTS (IC50 = 85.55 μg/mL). Validation trials confirmed the model's high predictive accuracy. While SFE-derived oils and powders exhibited robust antioxidant activity, they remained slightly below synthetic standards. Furthermore, Gas Chromatography / Mass Spectroscopy (GC/MS) analysis identified key bioactives - including α- bisabolol oxides, (E)-β-farnesene, and chamazulene - in accordance with European Pharmacopoeia standards, noting that maximum chamazulene recovery (7.12%) required a 4-hour steam distillation.

Behavior of Geopolymer Concrete Beams Strengthened using CFRP Sheets

2026-03-30

This study investigates the cyclic performance of beam–column joints fabricated with conventional reinforced concrete (RC) and metakaolin-based geopolymer concrete (GPC) with two distinct metakaolin replacement levels (15% and 100%), the beams are strengthened with external CFRP wrapping as a repair technique. The primary objective is to assess whether GPC can offer enhanced
structural performance and sustainability compared to ordinary Portland cement (OPC) concrete, particularly under reversed cyclic loading conditions that simulate earthquake excitations. Specimens representing three anchorage systems Type A with 90° hooked bars, Type B with straight bars, and Type C with cross bars providing mechanical interlock were prepared with identical geometric
dimensions and subjected to a constant axial load during testing. The experimental program involved detailed measurements of load–deflection behavior, ductility, energy absorption capacity, stiffness degradation, and failure modes. Results indicate that GPC beam–column joints exhibit improved energy dissipation and ductility compared to conventional RC joints, with the 100% metakaolin mix
outperforming the 15% metakaolin mix in terms of both initial cracking resistance and ultimate load capacity. Additionally, anchorage systems incorporating 90° hooks and cross bars demonstrated superior performance over straight bars, reducing bond-slip issues and enhancing cyclic stability. The integration of CFRP wrapping enhanced the structural integrity of the joints by delaying the onset of
macro-cracking and stabilizing internal reinforcement. However, the transition to high-displacement cycles eventually led to CFRP debonding, which limited the full potential of the strengthening scheme at peak drift levels. Microstructural analysis revealed that the denser matrix and enhanced bond characteristics of the optimized GPC mix contribute significantly to the improved cyclic behaviour.
These findings suggest that metakaolin-based geopolymer concrete, particularly with 100% metakaolin replacement, is a promising sustainable alternative for seismic applications, offering potential reductions in CO₂ emissions while maintaining or even enhancing structural performance under cyclic loading.