Powder Technology最新文献

The transient evolution of granules was studied to learn new details about the underlying mechanism for continuous wet granulation in a twin-screw extruder. Sieving and a new inline PAT for particle size development was used to gain these insights. The onset for steady state was established based on observing a consistent PSD, which occurred at five times the mean residence time of the process, over a range of degrees of fill (DF; 12–30 %). The early stages of startup for granulation were captured by the inline PAT, showing different stages of granule growth for particle sizes ranging from 102 to 2230 μm. The analysis found that conveying elements have a stronger influence on granule growth at a low DF whereas the kneading zone had a stronger influence on granule growth at a higher DF. This study presents new details on this black-box process while highlighting the unique value of PAT to twin-screw granulation.

This review paper examines the dynamics of snow accumulation on vehicle surfaces and its impacts on vehicle performance and safety. It focuses on the use of computational fluid dynamics (CFD) to model snow ingress in vehicle air intakes and its interactions with sensors in advanced driver assistance systems (ADAS). Central to these studies is the coefficient of restitution (COR), which measures the elastic properties of snow upon collision with vehicle surfaces. The paper provides an overview of various turbulence models, such as large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS), assessing their effectiveness in simulating the aerodynamic fields that affect snow trajectories. It critically reviews existing models and highlights recent experimental studies related to COR of snowflakes based on different impact velocities and particle conditions. The discussion on the practical implementation of these findings in automotive design underscores their importance in enhancing vehicle safety and reliability under extreme weather conditions.

In Chemical Mechanical Polishing (CMP) using ceria-based abrasives, a key challenge is maintaining particle stability to ensure consistent, reproducible, and predictable polishing results. Given the combined nature of CMP, involving both chemical reactions and mechanical abrasion, it is widely believed that during the polishing process, chemical compounds from the glass dissolve into the slurry, leading to changes in its chemical composition, which can affect stability and particle size distribution. However, these assumptions have primarily been based on simulations or speculative suggestions rather than direct experimental evidence. To investigate this further, experiments were conducted using three types of glass representing high, medium, and zero alkali content polished with both 400 nm and 80 nm ceria abrasives. A substantial increase in the slurry pH was observed when polishing soda-lime-silicate and borosilicate glass with 400 nm abrasives, whereas the pH remained stable when polishing fused silica glass. Notably, polishing with 80 nm abrasives did not affect the pH levels across the different glass types. Zeta potential measurements, particle size distribution, and real-time imaging provided insights into ceria particle aggregation and dispersion. Scanning Electron Microscopy (SEM) further confirmed changes in particle behavior. The findings of this study demonstrate that the polishing of alkali-containing glasses using larger ceria abrasives alters slurry chemistry and modifies particle size distribution. These findings provide new insights into the complex interactions between slurry chemistry, particle size, and glass composition in CMP, highlighting the need for careful control of abrasive properties during the process to ensure consistent and stable polishing performance.

Mechanical milling of the pyrophyllite ore leads to an increase in material chemical reactivity. This is a consequence of structural changes occurring during the milling process and depends on the milling time. This work aims to investigate structural changes caused by the mechanical milling of pyrophyllite ore using Raman spectroscopy for possible application in wastewater remediation. It was shown that the quartz bands at 122 cm⁻¹ or 459 cm⁻¹ could be references for tracking the phyllosilicate and calcite structural changes. The intensity ratio of quartz and phyllosilicate/calcite bands increases considerably with increasing milling time. Also, the Full Width at Half Maximum (FWHM) evolution of the 257 cm⁻¹, 701 cm⁻¹, and 1078 cm⁻¹ bands has a similar trend as the mentioned intensity ratio. Based on the obtained results, it can be concluded that Raman spectroscopy is a suitable tool for structural changes monitoring in this natural clay caused by mechanical milling.

The current understanding of the geotechnical behavior of lunar in-situ resources, particularly lunar regolith (LR), is significantly limited due to its scarcity. To address this gap, this research utilized the morphological characteristics of LR particles obtained from the Chang'E-5 (CE-5) mission to construct numerical simulants using the discrete element method (DEM). This approach was then employed to investigate the mechanical properties of LR. Firstly, high-definition lunar particle images from the CE-5 mission were selected to capture the morphological characteristics and grain size distribution. These morphological characteristics were linked with the rolling resistance parameter and incorporated into the three-dimensional (3D) micromechanical contact model. Additionally, a flexible boundary condition was employed in the triaxial simulation to ensure the evolution of strain localization. The relative particle translation gradient (RPTG) concept was utilized to capture the onset and development of strain localization during the shear process. The results indicated that the numerical lunar simulants can effectively reproduce the mechanical response of LR. Furthermore, at the particle scale, particle shape characteristics play a crucial role in particle rotation and translation during the shear process. This study may establish a foundation for lunar resource exploration and utilization techniques.

During maize harvesting, the mechanical action and suboptimal design of threshing systems often lead to kernel breakage and loss, which can reduce both maize quality and yield. This study introduces a novel rasp bar threshing element designed to minimize kernel loss. The effects of the structural parameters of this threshing element on its performance are analyzed using a flexible discrete element model of maize. Moreover, the performance of the novel threshing element is compared to that of a traditional threshing element, and the simulation results are verified through experimental tests. Test data shows that, compared to the traditional threshing element, the novel threshing element results in a relative decrease of 26.94 %, 21.95 %, and 27.05 % in the broken rate, unthreshed rate, and the entrainment loss rate, respectively. Finally, this research provides technical support for high-quality, low-loss maize production.