Particuology最新文献

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.

The increase in oily contaminated wastewater emissions has made it essential to develop efficient treatment approaches to mitigate its negative impact on the ecosystem and human health. In this research, a suspended catalyst photocatalytic membrane reactor (SPMR) is developed for simultaneous oil-water separation as well as pollutants degradation using ZnO as a photocatalyst and a submerged LED-UV light. A composite membrane unit was used in the reactor that was made of a polymeric layer and a superhydrophilic (SHPI) underwater oleophobic layer. The later was prepared by attaching ZnO nanoparticles (NP) on stainless steel mesh using the spraying method. The pure water flux of the composite membrane was comparable to that of the pristine polymeric membrane indicating minor resistance of the SHPI layer. For oil-water emulsion, water flux ∼1332 L m⁻² h⁻¹ was achieved at 20 kPa transmembrane pressure (TMP) with ∼99% oil separation efficiency. Using methylene blue dye (MB) decolourizations to assess simultaneous oil-water separation and pollutant degradation efficiencies, close to 86% dye decolourization and near complete oil water separation was achieved. The results suggest a promising potential of the proposed design for treatment of contaminated oily wastewater.

Lithium-rich cathode materials have garnered significant attention in the energy sector due to their high specific capacity. However, severe capacity degradation impedes their large-scale application. The employment of fast ion conductors for coating has shown potential in improving their electrochemical performance, yet the structural and chemical mechanisms underlying this improvement remain unclear. In this study, we systematically analyze, through first-principles calculations, the mechanism by which Li₂O-B₂O₃-LiBr (Hereafter referred to as LBB) coating enhances the electrochemical performance of the lithium-rich layered cathode material 0.5Li₂MnO₃·0.5LiNi_1/3Co_1/3Mn_1/3O₂ (Hereafter referred to as OLO). Our calculations reveal that the LBB coating introduces a more negative valence charge (average −0.14 e) around the oxygen atoms surrounding transition metals, thereby strengthening metal-oxygen interactions. This interaction mitigates irreversible oxygen oxidation caused by anionic redox reactions under high voltages, reducing irreversible structural changes during battery operation. Furthermore, while the migration barrier for Li⁺ in OLO is 0.61 eV, the LBB coating acts as a rapid conduit during the Li⁺ deintercalation process, reducing the migration barrier to 0.32 eV and slightly lowering the internal migration barrier within OLO to 0.43 eV. Calculations of binding energies to electrolyte byproducts HF before and after coating (at −7.421 and −3.253 eV, respectively) demonstrate that the LBB coating effectively resists HF corrosion. Subsequent electrochemical performance studies corroborated these findings. The OLO cathode with a 2% LBB coating exhibited a discharge capacity of 157.12 mAh g⁻¹ after 100 cycles, with a capacity retention rate of 80.38%, whereas the uncoated OLO displayed only 141.67 mAh g⁻¹ and a 72.45% capacity retention. At a 2 C rate, with the 2 wt% LBB-coated sample maintaining a discharge capacity of 140.22 mAh g⁻¹ compared to only 107.02 mAh g⁻¹ for the uncoated OLO.

The palladium-catalyzed Suzuki-Miyaura cross-coupling (SMC) reaction has received worldwide attention as a powerful and convenient synthetic tool for the formation of biaryl compounds. However, these reactions are highly dependent on the activity and stable of catalysts. Herein, the support morphology-dependent catalytic performance of SMC reactions was investigated. The truncated hexagonal bipyramid (α-Fe₂O₃-O) and rod-shaped morphologies of alpha-Fe₂O₃ (α-Fe₂O₃-R) were used as support to prepare PdCu nanoparticles (NPs) catalysts by NaBH₄ reduction method. For PdCu/α-Fe₂O₃-R catalysts, the smaller size of PdCu NPs and more low coordination Pd sites leading to its superior catalytic performance for SMC reactions. Furthermore, it can be easily recycled through centrifugation and reused several times without obvious loss on its catalytic performance. Identical location transmission electron microscopy method was used to investigate the structural evolution of PdCu/α-Fe₂O₃-R catalysts. The results found that its structure almost unchanged during the catalytic reaction.

Towards increasingly severe worldwide pollution of industrial solid waste red mud (RM) released from aluminum industry, constitutional valuable element Al has been successfully separated for a novel mild rotating hydrothermal synthesis (150 °C, 12 h, 5 Hz) of the uniform hierarchical porous flowerlike boehmite (γ-AlOOH) microspheres in the presence of appropriate urea, which exhibit distinctly small average diameter (1.52 μm) and narrow particle size distribution (PSD: 1.12–1.97 μm), as well as high specific surface area (129.37 m² g⁻¹). On the one hand, the rotating hydrothermal synthesis promotes the mass and heat transfer, enabling γ-AlOOH microspheres at a lower temperature within a shorter time. On the other hand, moderate rotation provides predominant shear force, rendering the uniform γ-AlOOH microspheres with small average diameter and narrow PSD. The optimal AlOOH–U2M-R5Hz microspheres demonstrate satisfactory adsorption performance for Congo Red (CR) and Methyl Blue (MB), with the maximum adsorption capacities of 602.4 and 1208.7 mg g⁻¹, respectively. Various isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich are utilized, adsorption kinetics are analyzed, adsorption mechanism is uncovered based on hydrogen bonding and electrostatic attraction. The increase in the temperature or the presence of coexisting cations facilitates the adsorption of CR, whereas coexisting anions weaken the adsorption of CR on the AlOOH–U2M-R5Hz microspheres. Furthermore, the excellent recycling performances and especially dynamic adsorption (retainment of removal efficiency of approx. 99.0% within 1000 min) as well as authentic water bodies (e.g. tap water and river water) simulated wastewater treatment undoubtedly indicate great practical applications of the AlOOH–U2M-R5Hz microspheres, towards cleaner aluminum production and cost-effective sustainable solution to anionic dye-bearing wastewater.

In pursuit of effective adsorption materials for malodorous gases such as H₂S and to broaden the utilization avenues of lignin waste, this study employed the direct pyrolysis method to synthesize three types of alkali lignin graphitized carbons, namely C-800, KC-700, and KEC-700. Among them, KEC-700 exhibits a high specific surface area of 1672.9 m²/g, significantly superior H₂S adsorption performance compared to other materials, an adsorption breakthrough time of up to 220 min, and a sulfur capacity of 67.1 mg/g. Structural analysis showed that the more oxygen-containing functional groups of lignin charcoal and the larger specific surface area facilitated the adsorption of H₂S. After reaching adsorption saturation, the degree of graphitization of lignin carbon diminishes. The H₂S adsorption products primarily manifest as elemental sulfur and sulfate within the pores of lignin carbon measuring less than 2 nm. Through thermal regeneration, the charcoal effectively eliminates the elemental sulfur adsorption product. Nevertheless, sulfate removal proved unsatisfactory, as the adsorption efficiency of KEC-700 following two thermal regenerations was approximately 41% of that observed for fresh samples.

The present research focuses on improving the prediction of rotating particle collisions. Current particle-surface collision models do not accurately predict the particle rebound when taking rotation into account. Experimental data, such as the studies by Gorham and Kharaz (2000), Buck, Tang, Heinrich, Deen and Kuipers (2017), and Dong and Moys (2006) show that the Tsuji, Oshima and Morikawa (1985) model is inaccurate due to the incorrect tangential coefficient of restitution assumption. Hoomans, Kuipers, Mohd Salleh, Stein, and Seville (2001) introduced a similar model to the work by Tsuji et al. (1985) which includes a tangential coefficient of restitution but is only in two dimensions and does not consider out of plane rebounds. This work re-derives the particle collision model from the impulse equations for binary collisions in 3D while considering rotating particles. The derived equations in this work compares well to experimental particle-surface impact studies. The implications of this model are seen by investigating erosion due to particle collision in a simple pipe bend. It is shown that Tsuji et al. (1985) over predicts the erosion. These small differences in particle trajectories between the present model and the Tsuji et al. (1985) model will grow in complex flows with multiple close range particle impacts leading to inaccurate erosion predictions which will negatively impact the design of turbomachinery and pneumatic pipes.