Solids

The electronic-structure traits of titanium (Ti), chromium (Cr), manganese (Mn), and nickel (Ni) doped-zinc sulfide (ZnS) through H₂O molecule adsorption were investigated using first-principles studies. A detailed study was performed using density functional theory (DFT) calculations at the CAM-B3LYP-D3/6-311+G (d,p) level to investigate how H₂O is captured by a ZnS, ZnSTi, ZnSCr, ZnSMn, or ZnSNi nanostructure. The shape of binding of hydrogen or hydroxyl groups to the surface of a ZnS, ZnSTi, ZnSCr, ZnSMn, or ZnSNi nanostructure could produce a weak signal close to the edge of the surface. This thought was accompanied by delving into the density of states, consisting of total, partial, and orbital-projected density of states, as well as electrostatic potential, for both the bare and water-covered surfaces of ZnS, ZnSTi, ZnSCr, ZnSMn, and ZnSNi. From this, it can be considered that Zn, Ti, Cr, Mn, and Ni in these complexes have a better capability to take in electrons when water is captured. These outcomes propose that the electronic properties of these complexes can be altered by controlling where water is absorbed on their surfaces. The target of this investigation is to detect routes to treat water and ameliorate the performance of titanium zinc sulfide, chromium zinc sulfide, manganese zin sulfide, and nickel zinc sulfide alloys as photocatalysts for wiping contaminants.

Nowadays, carbonized natural fiber composites are sustainable alternatives for electromagnetic wave absorption in unmanned aerial vehicles (UAVs). However, achieving a balance between electromagnetic performance, structural thickness, and weight is still difficult. This study, therefore, presents a multi-objective optimization framework for designing a lightweight radar-absorbing multilayer composite using a carbonized false banana fiber/Fe₃O₄ hybrid absorber. In this work, a four-layer sandwich panel was modeled in SOLIDWORKS 2017 and analyzed using full-wave electromagnetic simulation in ANSYS HFSS (R18.1) over the frequency range of 2–18 GHz. Layer thicknesses were optimized using a multi-objective particle swarm optimization (MOPSO) algorithm with three objectives: maximizing the frequency-averaged power absorptivity, minimizing panel mass, and minimizing total thickness. The objectives were handled simultaneously through Pareto dominance without predefined weighting coefficients, and a compromise solution was selected from the resulting Pareto-optimal set. The selected Pareto compromise was subsequently adjusted considering practical layer-thickness and manufacturability requirements, resulting in a 2/5/2/1 mm multilayer configuration with a total thickness of 10 mm. The resulting configuration achieved frequency-averaged power absorptivities of 0.6756 over 2–18 GHz and 0.8289 within the Ku-band, together with an effective absorption bandwidth of 3.2 GHz for power absorptivity above 90%. A minimum reflection coefficient magnitude of 0.0230 (corresponding to a peak power absorptivity of 99.95% at resonance) was obtained, with a minimum reflection loss of −32.75 dB. The optimized panel achieved a mass of 0.1725 kg, corresponding to a modest 1.42% reduction relative to an equal-footprint, equal-thickness monolithic carbon-fiber reference panel. These numerical results show the potential of combining a biomass-derived absorber with multi-objective optimization for the preliminary design of UAV-oriented radar-absorbing multilayer structures.

The Dion–Jacobson perovskite solid acid, HLaNb₂O₇, is an important intermediate in many topochemical reactions such as those involving ion exchange, intercalation, exfoliation, and grafting. Rietveld structure refinement of time-of-flight neutron diffraction data (7.66 K, P4/mmm, a = b = 3.8907(3) Å, c = 10.5068(9) Å) shows that protons bridging across the HLaNb₂O₇ interlayer serve to align LaNb₂O₇ blocks through NbO₆ apical oxygens. The oxygens are 2.54 Å apart, with the intermediate proton distributed over two half-occupied sites, and 1.15(10) Å from the closest oxygen. Such short strong hydrogen bonds are shorter (1.40 Å) than are typical for many known mixed metal oxide solid acids (ca. 2.8 Å–3.5 Å). Anisotropic refinement of the hydrogen thermal parameter reveals an elongation suggesting an active hydrogen that moves between the two oxygens, O–H…O ↔ O…H–O; DFT modeling supports this behavior, finding a minimal activation energy between two states; and infrared studies (FTIR) exhibit a broad low-energy band at ~1600 cm⁻¹, associated with the hydrogen resonance between the apical oxygens. These results are discussed in terms of structure, strong low-barrier hydrogen bonding, and proton mobility.