可相变的纳米析出相诱发亚稳低温钢的高延展性

纳米析出相在所有合金中都被用作额外的增强相,但大多数情况,特别是在低温环境下,纳米析出相的引入会严重降低材料的塑性和可加工性.这一强塑性倒置问题仍然亟待解决.基于此,本文发现了一种可相变的纳米析出相(TNP),通过其在变形过程的相变行为在亚稳基体中诱发了以微带和孪晶马氏体为主的多阶段变形机制.与不含TNP的低温钢相比,可持续的两阶段加工硬化能力使其在77 K下的屈服强度和均匀伸长率都能分别提高30%和65%.微带和析出相之间的交互作用不仅使微观结构得到动态细化,也将孪晶马氏体推迟至应变后期发生.此外,这一相变行为也可以缓解界面的错配应变,阻碍孪晶生长并获得更均匀的变形.这一研究结果证明了析出诱发塑性的创新机制,可为在极端环境下析出强化的应用提供新的方向.

Ultra-antifreeze,ultra-stretchable,transparent,and conductive hydrogel for multi-functional flexible electronics as strain sensor and triboelectric nanogenerator

Conductive hydrogels have become one of the most promising candidates for flexible electronics due to their excellent mechanical flexibility,durability of deformation,and good electrical conductivity.However,in real applications,severe environments occur frequently,such as extremely cold weather.General hydrogels always lack anti-freeze and anti-dehydration abilities.Consequently,the functions of electronic devices based on traditional hydrogels will quickly fail in extreme environments.Therefore,the development of environmentally robust hydrogels that can withstand extremely low temperatures,overcome dehydration,and ensure the stable operation of electronic devices has become increasingly important.Here,we report a kind of graphene oxide(GO)incorporated polyvinyl alcohol-polyacrylamide(PVA-PAAm)double network hydrogel(GPPDhydrogel)which shows excellent anti-freeze ability.The GPPD-hydrogel exhibits not only good flexibility and ultra-high stretchability up to 2,000%,but ensures a high sensitivity when used as the strain sensor at−50°C.More importantly,when serving as the electrode of a sandwich-structural triboelectric nanogenerator(TENG),the GPPD-hydrogel endows the TENG high and stable output performances even under−80°C.Besides,the GPPD-hydrogel is demonstrated long-lasting moisture retention over 100 days.The GPPD-hydrogel provides a reliable and promising candidate for the new generation of wearable electronics.

Flexible,stretchable,and transparent InGaN/GaN multiple quantum wells/polyacrylamide hydrogel-based light emitting diodes

Visualization is a direct,efficient,and simple interface method to realize the interaction between human and machine,whereas the flexible display unit,as the major bottleneck,still deeply hinders the advances of wearable and virtual reality devices.To obtain flexible optoelectronic devices,one of the effective methods is to transfer a high-efficient and long-lifetime inorganic optoelectronic film from its rigid epitaxial substrate to a foreign flexible/soft substrate.Additionally,piezo-phototronic effect is a fundamental theory for guiding the design of flexible optoelectronic devices.Herein,we demonstrate a flexible,stretchable,and transparent InGaN/GaN multiple quantum wells(MQWs)/polyacrylamide(PAAM)hydrogel-based light emitting diode coupling with the piezo-phototronic effect.The quantum well energy band and integrated luminous intensity(increased by more than 31.3%)are significantly modulated by external mechanical stimuli in the device.Benefiting from the small Young's modulus of hydrogel and weak Van der Waals force,the composite film can endure an extreme tensile condition of about 21.1%stretching with negligible tensile strains transmitted to the InGaN/GaN MQWs.And the stable photoluminescence characteristics can be observed.Moreover,the hydrogen-bond adsorption and excellent transparency of the hydrogel substrate greatly facilitate the packaging and luminescence of the optoelectronic device.And thus,such a novel integration scheme of inorganic semiconductor materials and organic hydrogel materials would help to guide the robust stretchable optoelectronic devices,and show great potential in emerging wearable devices and virtual reality applications.

Conspicuous cruciform silk decorations deflect avian predator attacks

Although camouflage as an effective antipredator defense strategy is widespread across animals,highly conspicuous color patterning is not uncommon either.Many orb-web spiders adorn their webs with extra bright white silk.These conspicuous decorations are hypothesized to deter predators by warning the presence of sticky webs,camouflaging spiders,acting as a decoy,or intimidating predators by their apparent size.The decorations may also deflect predator attacks from spiders.However,empirical evidence for this deflection function remains limited.Here,we tested this hypothesis using the X-shaped silk cruciform decorations built by females of Argiope minuta.We employed visual modeling to quantify the conspicuousness of spiders and decorations from a perspective of avian predators.Then,we determined actual predation risk on spiders using naïve chicks as predators.Spider bodies and decorations were conspicuous against natural backgrounds to the avian visual systems.Chicks attacked the spider main bodies significantly less frequently on the decorated webs than on the undecorated webs,thus reducing predation risk.When both spiders and decorations were present,chicks also attacked the spider main bodies and their legs or decorations,and not randomly:they attacked the legs or decorations sooner and more frequently than they attacked the main bodies,independent of the ratio of the surface area between the decoration and spider size.Despite the increase in detectability,incorporating a conspicuous cruciform decoration to the web effectively defends the spider by diverting the attack toward the decoration or leg,but not by camouflaging or intimidating,thus,supporting the deflection hypothesis.