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Objective: The flow channel distribution of polylactic acid in four screw extruder with different screw arrangement was studied. Methods: The three-dimensional modeling software Solidworks was used to establish the screw model and the corresponding fluid region model under the arrangement of one-word screw, four-square screw and encircle screw. Numerical simulation was carried out by the simulation software Polyflow. Results: The screw arrangement of monotype and surround type had better pressure building ability and distribution mixing ability than the square arrangement, and the square arrangement had weaker transport ability of polylactic acid. Conclusion: The four-screw extruder with one-line screw arrangement has a good effect on the processing of PLA.

Objective: To investigate the effect of the screw configuration on the polylactic acid flow field on the structural parameters of the screw on the end face of the screw in the meshing counter rotating twin screw extruder. Methods: The theoretical model of the heterodirectional double-ended threaded element was established by Solidworks software and the geometry of the threaded element after adjusting the structural parameters in two different ways. The established three-dimensional model was imported into Gambit software for meshing, and then Polyflow software was applied to the flow field simulation calculation. Finally, the flow field distribution results were extracted by Fieldview software, and the effects of the adjustment of the structural parameters on the end surface of the threaded element during correction were compared and analyzed on the shear rate field, viscosity field and speed field. Results: The structural parameters of the threaded element during correction will affect the polylactic acid flow field after being adjusted in two ways. The two adjustment methods of structural parameters have reduced the shear rate gradient in the runner to varying degrees, and the first method has also caused the viscosity of the polymer lactic acid in the runner to be reduced. Conclusion: From the perspective of the influence on the shear rate field, viscosity field and speed field, the threaded element adjusted by mode one is more conducive to extrusion, while the solid configuration of the threaded element adjusted by mode two is closer to the theoretical configuration of the threaded component.

Objective: Explore the effects of different combinations of forward screw elements in the melt conveying section on the melt conveying characteristics of reverse screw elements. Methods: Two different models were constructed by changing the lead, using SolidWorks software to establish a three-dimensional model, and using Polyflow software to numerically simulate the extrusion process of the two models in the melt conveying section. The effects of the screw groove width and screw edge thickness of the screw elements on the flow field under different lead lengths and the changes in the flow field at different rotational speeds were analyzed, and the effects of rotational speed on the material mixing were verified through experiments. Results: The constructed model can allow the melt to pass through the reverse threaded element. At the same screw speed, the pressure building capacity and conveying capacity of model one constructed from large lead screw elements were stronger than that of model two constructed from small lead screw elements. Model one was superior to Model two in terms of decentralized mixing ability, and weaker than Model two in terms of distributed mixing ability. Under the same pressure difference at both ends, increasing the rotational speed could improve the dispersion and mixing effects of materials. Conclusion: Using model one in the improved processing of polylactic acid and increasing the rotational speed of the screw can further crush the material and improve the quality of the extrusion.

Application of silicon‐based anodes is significantly challenged by low initial Coulombic efficiency (ICE) and poor cyclability. Traditional pre‐lithiation reagents often pose safety concerns due to their unstable chemical nature. Achieving a balance between water‐stability and high ICE in prelithiated silicon is a critical issue. Here, we present a lithium‐enriched silicon/graphite material with an ultra‐high ICE of ≥110 % through a high‐stable lithium pre‐storage methodology. Lithium pre‐storage prepared a nano‐drilled graphite material with surficial lithium functional groups, which can form chemical bonds with adjacent silicon during high‐temperature sintering. This results in an unexpected O−Li−Si interaction, leading to in situ pre‐lithiation of silicon nanoparticles and providing high stability in air and water. Additionally, the lithium‐enriched silicon/graphite materials impart a combination of high ICE, high specific capacity (620 mAh g−1), and long cycling stability (>400 cycles). This study opens up a promising avenue for highly air‐ and water‐stable silicon anode prelithiation methods. [ABSTRACT FROM AUTHOR]

Large-geometry secondary ion mass spectrometry (LG-SIMS) is routinely used to determine the elemental and isotopic compositions, thanks to its high sensitivity and in situ micro-analysis capability. Its large volumes of transfer and coupling column, however, might bring low vacuum and high background of volatile elements (esp. H), which hampers its application in ultralow H2O content measurement. In this study, we report a modified analytical procedure to accurately analyze samples with ultralow-level H2O content by using a LG-SIMS of type CAMECA IMS 1280-HR. Based on four new water content working reference materials of quartz glasses with H2O contents ranging from ca. 0 to 39 ppm, the estimated detection limit of LG-SIMS is 0.15 ppm for H2O. This ultralow detection limit is achieved mainly by the intrinsic high sensitivity of the instrument and the conjunctive usage of a stabilized temperature-controlled cooling trap device and a novel tin–bismuth alloy mount preparation technology, which are able to maintain a vacuum pressure at 1.7 × 10−9 mbar in the analysis chamber. Based on these new improvements, our approach can potentially become a routine choice for analyses of H2O content and oxygen–hydrogen isotopes for (extra)terrestrial materials with ultralow-level water content. [ABSTRACT FROM AUTHOR]