ABSTRACT:Micrometer-and nanometer-Al 2 O 3 -particlefilled poly(phthalazine ether sulfone ketone) (PPESK) composites with filler volume fractions ranging from 1 to 12.5 vol % were prepared by hot compression molding. We evaluated the tribological behaviors of the PPESK composites with the block-on-ring test rig by sliding PPESK-based composite blocks against a mild carbon steel ring under dry-friction conditions. The effects of different temperatures on the wear rate of the PPESK composites were also investigated with a ball-on-disc test rig. The wear debris and the worn surfaces of the PPESK composites were investigated with scanning electron microscopy, and the structures of the PPESK composites were analyzed with IR spectra. The lowest wear rate, 7.31 ϫ 10 Ϫ6 mm 3 N Ϫ1 m Ϫ1 , was obtained for the composite filled with 1 vol %-nanometer Al 2 O 3 particles.The composite with nanometer particles exhibited a higher friction coefficient (0.58 -0.64) than unfilled PPESK (0.55). The wear rate of 1 vol %-nanometer-Al 2 O 3 -particle-filled PPESK was stable and was lower than that of unfilled PPESK from the ambient temperature to 270°C. We anticipate that 1 vol %-nanometer-Al 2 O 3 -particle-filled PPESK can be used as a good frictional material. We also found that micrometer-Al 2 O 3 -particle-filled PPESK had a lower friction coefficient at a filler volume fraction below 5%. The filling of micrometer Al 2 O 3 particles greatly increased the wear resistance of PPESK under filler volume fractions from 1 to 12.5%.
There is currently intense research interest in silicon based anodes in lithium‐ion batteries. Modification approaches for nano‐sized silicon materials are popular, while much less attention has been paid on irregular bulk silicon particles. Here, we report that soft multiwall carbon nanotube membranes could be functioned as a shield on low‐cost micro‐sized silicon anodes to improve the cycling stability. The micro‐sized silicon could deliver a high reversible capacity of over 1000 mAh g−1 after 50 cycles at 0.36 A g−1 with the protection of a soft multiwall carbon nanotube membrane. Furthermore, the capacity could also be retained at ∼610 mAh g−1 at 0.5 A g−1 after 1200 cycles. The much improved performance upon cycling is mainly attributed to the alleviation of the large volume change. This strategy has also been proved effective in traditional nano‐silicon anodes, as a quite high capacity of about 5 mAh cm−2 could be obtained after 200 cycles. Overall, simply using a soft multiwall carbon nanotube membrane is a so far overlooked strategy, which is effective for improving performance of silicon anodes.
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