As a polycrystalline fiber, continuous zirconia (ZrO 2 ) fiber used at high temperatures will cause grain coarsening and strength degradation due to grain growth. In order to suppress the grain coarsening, zirconium carbide (ZrC) and carbon were introduced into ZrO 2 continuous fibers by pack carburizing , and ZrC/ZrO 2 composite fibers with a radial gradient were subsequently prepared. Due to the pinning effect of ZrC or carbon on the grain boundary, the movement of the grain boundary is limited. The composite fibers obtained in an argon atmosphere at 1400 °C exhibited fine grain, compact micromorphology, and a tensile strength of 784 MPa. The formation process of the composite fiber was accomplished by the interaction of external graphite carbon and internal residual carbon with ZrO 2 . This work provides a simple and economical method for preparing carbide composite fibers.
Yao-feng Mao,Qian-qian He,Jian Wang,Chuan-hao Xu,Jun Wang,Fu-de Nie
As a typical energetic composite, polytetrafluoroethylene (PTFE)/aluminum (Al) has been widely applied in explosives, pyrotechnics, and propellants due to its ultra-high energy density and intense exothermic reaction. In this work, the radial gradient (RG) structure of PTFE/Al cylinders with three different PTFE morphologies (200 nm and 5 μ m particles and 5 μ m fiber) and content changes are prepared by 3D printing technology. The effect of radial gradient structure on the pressure output of PTFE/Al has been studied. Compared with the morphology change of PTFE, the change of component content in the gradient structure has an obvious effect on the pressure output of the PTFE/Al cylinder. Furthermore, the relationships of the morphology, content of PTFE and the combustion reaction of the PTFE/Al cylinder reveal that the cylinder shows a more complex flame propagation process than others. These results could provide a strategy to improve the combustion and pressure output of PTFE/Al.
Sida Xie,Ningxin Chen,Jie Deng,Ying-Jie Zhu,Long Cheng,Dandan Li,Heng Li,Zhaohui Wang
Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility, excellent manufacturability, and strong interfacial compatibility. However, their widespread applications are hindered by low ionic conductivity at room temperature and lithium dendrite growth. Herein, we report a novel solid-state composite membrane electrolyte design that combines the vertically aligned channel structure and copolymer with a radial gradient composition. Within the vertically aligned channels, the composition of poly(vinyl ethylene carbonate-co-poly(ethylene glycol) diacrylate) (P(VEC-PEGDA) varies in a gradient along the radial direction: from the center to the wall of vertically aligned channels, the proportion of vinyl ethylene carbonate (VEC) in the copolymer decreases, while the proportion of poly(ethylene glycol) diacrylate (PEGDA) increases accordingly. It can be functionally divided into a mechanical-reinforcement layer and a fast-ion-conducting layer. The resulting solid-state composite membrane electrolyte achieves a high critical current density of 1.2 mA cm −2 and high ionic conductivity of 2.03 mS cm −1 at room temperature. Employing this composite membrane electrolyte, a Li//Li symmetric cell exhibits stable cycling for over 1850 h at 0.2 mA cm −2 /0.2 mA h cm −2 , and a Li//LiFePO 4 (LFP) battery maintains 77.3% capacity retention at 2 C after 300 cycles. Our work provides insight into the rational design of safer and more efficient solid-state batteries through electrolyte structural engineering.
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