Particuology最新文献

In powder-bed-based additive manufacturing, the quality of the powder bed is closely related to the geometry of the blade used during the powder spreading process. In this study, the spreading process with the vertical blade, inclined blade, and round blade with different radii was performed by discrete element method to investigate the effects of blade geometry on powder spreading. The results show that at the same spreading parameters, the round blade caused the highest density than inclined blade and vertical blade. Increasing the round blade radius can improve the packing density of the powder bed, but it has little effect on the uniformity. The increase in packing density is related to the transitional smoothness of the blade surface at the entrance of the powder bed. The smoother the shape transition of the blade surface at the powder bed entrance, the powders enter the powder bed more gently, so more powders enter the powder bed, resulting in higher packing density. The results may provide suggestions for improving the laser melting process.

This work investigates the heat transfer characteristics of particle clusters under the effects of the complex properties of supercritical water (SCW). It analyzes the heat transfer characteristics of sub-particles and the average heat transfer characteristics of particle clusters. The results reveal a phenomenon of shifting positions of high specific heat regions. It led to variations in the dimensionless heat transfer coefficient distribution. Furthermore, the results indicate that as the heat transfer process strengthens, the effects of variations in property distribution on heat transfer tends to stabilize. Based on this conclusion, the effects of variations in property distribution on heat transfer are categorized into Stable Effects Region and Non-Stable Effects Region. By utilizing the principles of fluid flow-heat transfer coupling and similarity, a heat transfer prediction model for particle clusters in SCW is established.

Water pollution caused by organic dyes is a critical environmental issue. Although activated carbon (AC) is commonly used for dye adsorption, its effectiveness is limited by challenges in separation and regeneration. To address these limitations, a convenient recyclable magnetic activated carbon (MAC) was fabricated via co-precipitation and calcination method, serving as adsorbent and catalyst for methyl orange (MO) removal through a Fenton-like degradation process. Characterization techniques, including XRD, FTIR, SEM and TEM, confirmed that Fe₃O₄ nanoparticles (10–20 nm) were uniformly dispersed on AC surface. The MAC maintaining a high surface area (997 m²/g) and pore volume (0.795 cm³/g) and exhibited superparamagnetic properties with a saturated magnetization of 5.52 emu/g, enabling effective separation from aqueous solutions by magnet. Batch adsorption studies revealed that MO adsorption onto MAC followed pseudo-second-order kinetic and Freundlich isotherm model, with a maximum adsorption capacity of 205 mg/g at 25 °C. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. Simultaneous degradation of MO and in-situ regeneration of MAC were achieved via Fenton-like reaction using sodium persulfate (PS). Under a PS concentration of 9 mmol/L, the MO removal efficiency near 95% after 60 min, with a total organic carbon (TOC) reduction of 83.1%. The reaction of Fe₃O₄ and oxygen functional groups on AC surface with PS facilitated the generation of ${\text{SO}}_4^{•-}$, thereby enhancing catalytic degradation of MO. The degradation efficiency improved as the temperature increased from 25 °C to 45 °C. Cycle tests demonstrated that the MO removal efficiency of MAC remained above 90% after 5 cycles of regeneration. Overall, this study highlights the potential of MAC for efficient removal of organic dyes from water through the coupling of adsorption and Fenton-like degradation, providing a promising solution for addressing water pollution challenges.

The mortality rate of neurological disorders is increasing globally, and natural antioxidant geniposidic acid (GPA) holds great potential in the treatment of neuronal oxidative damage. Nevertheless, its inherent instability constrains its pragmatic utilization. Herein, we introduced a drug delivery system capable of protecting unstable natural active compounds from degradation. Among the various methods for preparing drug-loaded microspheres, the emulsification-solvent evaporation technique is one of the most commonly employed due to its efficiency and simplicity. Nevertheless, this method results in microspheres with heterogeneous particle sizes. To address this limitation, we developed a two-step emulsification method involving stirring and homogenization. Using the biocompatible, synthetic, biodegradable polymer polycaprolactone (PCL) as the drug delivery carrier, we prepared GPA-loaded PCL microspheres via the two-step emulsification method. The results demonstrated that the microspheres possessed uniform particle size (polydispersity index = 0.12), excellent drug loading capacity (∼4.86%), sustained drug release profiles (∼68.55% in 264 h), and biocompatibility (cell viability >85%). The in vitro tests showed that the microspheres exerted antioxidant effects by scavenging reactive oxygen species (ROS) induced by oxidative stress, thereby protecting neuronal cells from oxidative damage. This work presents a promising new approach for the treatment of neuronal oxidative damage.

In the industry of production of high-density fiberboards without adhesive, applying vibration to the particle packing system before pressing and molding is an effective way to improve the uniformity of particle packing and reduce porosity. In this work, physical experiments combined with numerical simulations are used to systematically investigate the packing structure behavior of wood powder particles under different vibration conditions. Macroscopic and microscopic properties such as porosity, coordination number, radial distribution function, and contacts are characterized and analyzed. The results indicate that when the vibration frequency is 72 Hz and the vibration amplitude is 1 mm, the porosity of wood powder particles closely packed is minimized. The results of the Discrete Element Method show that the distribution of the coordination number is approximately normal. As the vibration conditions change, the packing structure becomes tighter, but the main peak of the radial distribution function becomes blurred or even disappears. Vibration does not significantly change the type of contact in the packing structure. The conclusions can provide more comprehensive vibration conditions and microscopic theories for the uniform spreading of wood powder particles before pressing, ensuring that the finished panels have excellent mechanical and physical properties.

There are currently no reports about clusters in the supercritical water circulating fluidized bed (SCWCFB). Simulations were conducted to investigate the numbers, diameters, aspect ratios, circularity, and orientation angles of cluster in the riser of SCWCFB via two-fluid model across different flow velocities, solid circulation rates, pressures, and temperatures. The results show that cluster numbers are mainly between 10 and 80 per m². Clusters are more at the bottom but less at the top, and more near the wall but less at the center. Cluster diameters are mainly between 0.2 and 0.5 times the bed diameter. Clusters are large at the bottom but small at the top, and large at the center but small near the wall. Cluster aspect ratios are mainly between 0 and 1, indicating that most clusters have shorter width than their heights. Stream-like clusters are more likely to appear near the walls, and clusters at the center of the riser are more likely to be arch-shaped. Cluster circularity is mainly between 0.2 and 0.4, suggesting that the shapes of clusters are far from the roundness. The absolute values of cluster orientation angles are mainly between 75° and 90°, indicating that most clusters move in the vertical attitudes. High fluid velocities may facilitate cluster coalescence.

A Discrete Element Method model, including interparticle cohesive forces, was calibrated and validated to develop a tool to predict the powder layer’s quality in the powder bed fusion process. An elastic contact model was used to describe cohesive interparticle interactions. The surface energy of the model particles was estimated by assuming that the pull-off force should provide the strength of the material evaluated at low consolidation with shear test experiments. The particle rolling friction was calibrated considering the bulk density of the layer produced by the spreading tool. The model was validated with the experiments by comparing the wavelet power spectra obtained with the simulations with those of the experimental layers illuminated by grazing light. The calibration proposed in this study demonstrated superior performance compared to our previous methods, which relied on measuring the angle of repose and unconfined yield strength.