Numerical and Experimental Investigation on the Self-Healing Potential of Interpenetrating Metal–Ceramic Composites

An interpenetrating metal ceramic composite (IMCC) has been investigated regarding the potential as well as the feasibility of self-healing. Triggered by heating, cracks in the damaged composite located mainly in the Al₂O₃ ceramic or at the interface could be filled and closed by the liquid AlSi10Mg metal alloy. This healing procedure promises to reduce stress concentrations at crack tips and to improve the mechanical properties compared to the predamaged composite. Two different numerical approaches have been introduced to investigate this assumption and the potential of self-healed IMCCs for a best case scenario: 1) A simple 2D model to analyze the reduction of stress concentrations in front of a crack tip within the ceramic due to healing and 2) a 3D model based on CT-scan reconstructed microstructures to study how macroscopic mechanical properties can be restored depending on the amount of predamage. Further, the self-healing approach has been investigated experimentally for the same composite. Despite the fact that experimental self-healing of the investigated IMCC is only moderately feasible so far, the study shows the great potential that can still be exploited in order to extend the service life time of IMCC engineering components.     

Glycerol-modified poly(vinyl alcohol)/poly(ethylene glycol) self-healing hydrogel for artificial cartilage

Poly(vinyl alcohol) (PVA) hydrogels have shown potential applications in bionic articular cartilage due to their tissue-like viscoelasticity, good biocompatibility and low friction. However, their lack of adequate mechanical properties is a key obstacle for PVA hydrogels to replace natural cartilage. In this study, poly(ethylene glycol) (PEG) and glycerol were introduced into PVA, and a PVA/PEG–glycerol composite hydrogel was synthesized using a mixing physical crosslinking method. The mechanical properties, hydrophilicity and tribological behavior of the PVA/PEG–glycerol hydrogel were investigated by changing the concentration of glycerol in PEG. The results showed that the tensile strength of the hydrogel reached 26.6 MPa at 270% elongation at break with 20 wt% of glycerol plasticizer, which satisfied the demand of natural cartilage. In addition, the excellent hydrophilicity of glycerol provides good lubricating properties for the composite gel under dry friction. Meanwhile, self-healing and cellular immunity assays demonstrated that the composite gel could have good self-healing ability and excellent biocompatibility even in the absence of external stimuli. This study provides a new candidate material for the design of articular cartilage, which has the potential to facilitate advances in artificial joint cartilage repair. © 2022 Society of Industrial Chemistry.     

Multi-Healable,Mechanically Durable Double Cross-Linked Polyacrylamide Electrolyte Incorporating Hydrophobic Interactions for Dendrite-Free Flexible Zinc-Ion Batteries

Flexible aqueous zinc-ion batteries (ZIBs) are considered as one of the most promising energy storage candidates for wearable electronics, owing to their environmental friendliness, low cost, high safety, and high theoretical capacity. However, the practical application of flexible ZIBs is significantly impeded by the Zn dendrite growth and the poor mechanical endurability at the electrolyte–electrode interface. Mechanically durable hydrogel electrolyte with dendrite growth restriction and self-healing ability is highly desirable to improve the durability and extend the lifetime of the flexible ZIBs. However, it is still a big challenge to simultaneously endow hydrogel electrolytes with all necessary properties. Herein, multi-healable and mechanically durable hydrogels are fabricated by the synergy effect of strong chemical cross-linking and dynamic physical hydrophobic associations. The obtained double cross-linked polyacrylamide electrolyte (PAAm-O-B) has good tensile strain, strength, and stable electrochemical performance, with tensile strength up to 75 kPa, high self-healing efficiency up to 50 broken-healed cycles and lifespan up to 900 h dendrite inhibition behavior. The flexible Zn//MnO₂ batteries using PAAm-O-B hydrogel electrolytes exhibit good mechanical durability with high specific capacity and long cycle lifespan even under 1000 bending deformations and superior self-healing ability.     

超疏水表面服役稳定性的研究进展

目的 超疏水表面脆弱、耐久性差且难以修复等情况一直是超疏水涂层在实际应用过程中面临的最大挑战，通过总结和分析找到解决这一问题的方法。方法 本文对超疏水涂层可能遇到的破坏和对应的耐久性类型进行了系统分析和总结，针对每种耐久性类型分别归纳出多种测试方法并对每种测试方法对应的控制参数进行了详细阐述，对不同耐久性类型和测试方法也分别进行了详细的举例说明。结果 针对超疏水涂层耐久性差的问题，本文总结出两类提高表面耐久性的方法，分别是是提高超疏水涂层的机械稳定性和赋予涂层良好的自修复能力。提高涂层机械耐久性的方法包括构造多层次分层结构、提高涂层与基底的黏结能力、构建自相似超疏水表面，记忆建立“盔甲”结构等。自修复能力包括粗糙结构的自修复、低表面能物质的自修复、整体的自修复。结论 有了强机械稳定性，超疏水涂层在面对破坏时也有了更好的抵御能力。而具备良好的自修复能力，则可以保障涂层在被破坏后仍可以恢复至超疏水状态。此外，本文还对超疏水涂层的未来发展进行了展望，即找到一种满足各种耐久需求、低成本、适合大面积生产的超疏水表面制备方法。