This study explores the thermodynamic and kinetic properties of CeO₂ nano-fuels, with a particular focus on the influence of nanoparticle additives on the diffusion and thermal conductivity of C14-based fuel systems. Using molecular dynamics simulations and the COMPASS force field, we model the interactions between C14 molecules and CeO₂ nanoparticles, varying nanoparticle size and concentration. Our results reveal that the inclusion of CeO₂ nanoparticles leads to significant enhancements in both thermal conductivity (increasing by 9.8–23.6%) and diffusion coefficients (increasing by approximately 140%) within the 20 °C to 100 °C temperature range. These improvements are attributed to the interactions between nanoparticles and fuel molecules, which facilitate more efficient energy and mass transport. Notably, nanoparticles with smaller sizes (0.2 nm and 0.5 nm) exhibit more pronounced effects on both the thermodynamic and kinetic properties than larger nanoparticle analogs (20 nm and 50 nm). The study also highlights the temperature-dependent nature of these properties, demonstrating that nanoparticle additives enhance the fuel’s thermal stability and diffusion behavior, particularly at elevated temperatures. This work provides valuable insights into the optimization of nano-fuel systems, with potential applications in enhancing the performance and efficiency of diesel combustion and heat transfer processes.

Linear ultrasonic techniques often exhibit insufficient sensitivity to small defects in composite materials. Furthermore, current deep learning approaches for porosity detection rely heavily on hand-crafted features and suffer from limited generalization capabilities when trained on small datasets. To address these challenges, this paper proposes a novel nonlinear ultrasonic detection method for composite porosity based on Continuous Wavelet Transform (CWT) and a KAN-ResNet50 architecture, enhanced by simulated data augmentation. First, a random pore model with varying porosity levels is constructed based on random medium theory. COMSOL Multiphysics is then utilized to simulate and extract the corresponding nonlinear ultrasonic response signals. Subsequently, CWT is applied to both simulated and experimental ultrasonic signals, converting them into time-frequency images to construct a comprehensive dataset for porosity classification. An ImageNet-pretrained ResNet50 model serves as the backbone network, with its top-level residual blocks fine-tuned. Notably, a Kolmogorov-Arnold Network (KAN) replaces the traditional fully connected layer as the classification head to form the final porosity evaluation model. Experimental results demonstrate that the proposed method achieves an average classification accuracy of 91.15% across four types of porosity samples on the test set, verifying its effectiveness. This study provides a highly feasible, automated, and intelligent approach for the non-destructive evaluation of composite porosity, significantly reducing the reliance on large-scale experimental samples.

Ablative pulsed plasma thruster (APPT)-induced fluorocarbon contamination severely degrades microsatellite optics and solar panels, but the spatial heterogeneity of its chemo-optical properties and underlying plasma-film mechanisms remain poorly understood. In this work, X-ray photoelectron spectroscopy (XPS), scanning probe microscopy (SPM), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) spectrophotometry were used to characterize the chemical structure, morphology, thickness, and chemo-optical properties of PTFE-derived fluorocarbon films, while high-speed imaging and triple Langmuir probe diagnostics were used to map plume conditions governing film formation. The film F/C ratio (0.6–1.0) is far lower than that of pristine PTFE (2.0), controlled by competition between energetic ion sputtering and delayed neutral C₂F₄ deposition. In the electrode-perpendicular plane, the F/C ratio reaches a minimum ~0.6 at 30°, corresponding to a transmittance of <20% at 550 nm; anode-side films exhibit lower F/C ratios and transmittance yet higher reflectance than cathode-side counterparts. Films in the electrode-parallel plane show quasi-symmetric bond distributions and higher F/C ratios and transmittance, with F/C minima at ±15°. By correlating plasma anisotropy (cathode-biased electron density and anode-biased electron temperature) with film chemistry and optics, we identify this ion–neutral competition as the origin of angle-dependent film properties. This work provides design guidelines: optics within 30° of the thruster axis in the perpendicular plane require active protection, enabling quantitative anisotropic contamination risk assessment for microsatellites.