Particle size and doping affect the surface energetics of ZnO nanoparticles and their electronic energy-level alignment. This study investigates size-dependent work functions in pristine ZnO and Al-doped ZnO nanoparticles and estimates the corresponding conduction- and valence-band-edge positions. Atomic force microscopy and Kelvin probe force microscopy were used to correlate particle size with local work function calculated from calibrated contact potential difference measurements. Optical band gaps estimated from ultraviolet visible absorption spectra using Tauc analysis were 3.050 eV for ZnO and 3.185 eV for Al-doped ZnO. Twelve nanoparticles were examined per material, with AFM measurements showing sizes of 5.7–29.3 nm for ZnO and 7.1–25.2 nm for Al-doped ZnO. Work function decreased approximately linearly with increasing particle size, with slopes of −1.871 and −3.912 meV nm−1 and coefficients of determination of 0.956 and 0.961, respectively. The Al-doped ZnO sample exhibited a slope magnitude approximately 2.09 times that of pristine ZnO. Assuming that the Fermi level coincides with the conduction-band minimum, combining the optical gaps with the work-function measurements yielded estimated band edges that shifted toward less negative energies with increasing particle size. The study provides a quantitative particle-level comparison of size-dependent work functions and estimated band edge trends in ZnO and Al-doped ZnO nanoparticles. These findings establish a correlation between nanoparticle size and work function in the investigated ZnO and Al-doped ZnO samples and provide a framework for estimating size dependent conduction and valence band edge positions.
The synthesis of boron nanoparticles (BNPs) at different temperatures using the dual-pulsed laser ablation (DPLA) method was investigated. A Q-switched Nd: YAG laser with dual wavelengths of 532 and 1064 nm was used to ablate a solid boron target. BNP growth with 0.5% Ni and 0.5% Co catalysts was facilitated through a vapor-solid process in a quartz tube furnace under controlled temperature and pressure with flowing argon (Ar). X-ray diffraction (XRD) revealed diffraction features consistent with crystalline boron structures, with several reflections corresponding to α-boron. High-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM) revealed nanoscale particles with temperature-dependent morphology. Image analysis showed mean particle diameters of 6.24, 3.68, and 1.49 nm for BNPs synthesized at 450, 550, and 650 °C, respectively. The corresponding lattice distances were 0.37, 0.35, and 0.33 nm, indicating potential relevance to hydrogen storage applications. Raman spectroscopy revealed characteristic vibrational modes associated with the BNPs. UV–Vis spectroscopy, Tauc analysis, and four-point probe measurements were used to investigate their optical and electrical properties. The optical bandgap increased from 3.72 to 3.80 eV with increasing synthesis temperature, while electrical conductivity increased from 0.198 to 0.249 S cm−1, with approximately linear current–voltage characteristics. These results demonstrate temperature-dependent structural, optical, and electrical characteristics of the synthesized BNPs and their relevance to semiconductor-related applications. Furthermore, a resistive memory device incorporating the 650 °C BNPs into a PVP matrix exhibited an ON/OFF current ratio of approximately 7 × 104, endurance exceeding 104 cycles, and retention of up to 106 s. These results demonstrate the feasibility of the synthesized BNPs for nonvolatile resistive memory applications.
Wood–carbon fiber-reinforced thermoplastic (CFRTP) laminates are promising sustainable materials for lightweight structural components and wood-forming applications because they combine environmental benefits of wood with the high mechanical performance, recyclability, and reprocessability of CFRTPs. However, the influence of laminate configuration on the flexural behavior of wood–CFRTP laminates remains unclear. In this study, thin-layer laminated panels composed of wood and CFRTP tapes were fabricated with different stacking configurations, and their flexural properties and failure behaviors were evaluated by conducting three-point bending tests. The incorporation of CFRTP increased the density and flexural performance of the panels compared with those of wood alone; however, the flexural strength and modulus were significantly influenced by the stacking configuration rather than only by CFRTP content.Among the wood–CFRTP laminates, the [Wep0/CF04]T configuration exhibited the highest flexural strength (625 MPa) and specific flexural strength (565 MPa cm3 g−1). In contrast, specific two-layer configurations exhibited remarkably large deformation without catastrophic failure. Similar deformation behavior was observed in laminates fabricated using higher-density hardwoods, highlighting the importance of the compressive properties of the wood layer. Neutral-axis analysis suggested that the placement of wood layer on the compressive side altered the stress distribution and contributed to failure suppression. Although the effects of the wood–CFRTP interface require further investigation, these findings establish stacking configuration as a critical design parameter for controlling both flexural performance and deformability. The enhanced bendability also suggests potential applications beyond lightweight structural components, including novel wood-forming processes under dry conditions at room temperature.
Sandwich panels with architected lattice cores offer high stiffness-to-weight efficiency, yet their low-velocity impact performance remains strongly governed by core material behavior rather than geometry alone. While carbon nanotube reinforcement has been widely studied in bulk polymer composites, its role as an injected filler within additively manufactured lattice sandwich cores remains insufficiently understood. The novelty of this work lies in the architecture-level experimental investigation of 3D-printed polylactic acid (PLA) X-frame sandwich panels filled with epoxy reinforced by controlled multi-walled carbon nanotube (MWCNT) concentrations (0–1.25 wt%), and in the systematic evaluation of how CNT loading governs crack propagation, through-thickness damage transmission, and failure morphology under low-velocity impact. Low-velocity drop-weight tests were conducted at impact energies of 22.34 J and 37.23 J (impact velocities of 1.71 m/s and 2.21 m/s). Damage evolution was quantified using front- and back-face macro-crack length measurements and indentation diameter analysis. The results reveal a pronounced non-linear dependence on CNT content. Intermediate CNT concentrations (0.5–0.75 wt%) produce the most damage-tolerant response, characterized by highly localized indentation and complete suppression of back-face cracking at both impact energies. In contrast, unreinforced panels exhibit extensive through-thickness cracking, while excessive CNT loading (1.25 wt%) restores brittle splitting behavior. Furthermore, increasing impact energy induces a shift from global splitting to more localized deformation in certain compositions, highlighting the energy-dependent nature of failure mechanisms. Overall, the study identifies an effective CNT concentration window specific to resin-filled X-frame sandwich cores and provides architecture-level design guidance for lightweight impact-resistant sandwich structures where minimizing damage footprint and suppressing rear-face damage are critical.
