Static recrystallization and grain growth during annealing of an extruded Mg-Zn-Zr-Er magnesium alloy

Microstructure stability is essential to maintain a fine grain structure for an alloy throughout its processing.The effects of Er addition and its existing form on the static recrystallization and grain growth during annealing of an extruded Mg-1.5Zn-0.6Zr magnesium alloy were studied in this paper.The results showed that microstructure stability was much improved by Er addition and the best thermability was obtained in 2 wt.%Er-containing alloy.For the incomplete dynamic recrystallization(DRX)microstructures extruded at a lower temperature of 350℃,Er addition increased the resistance of static recrystallization;and for the complete DRX microstructures extruded at a relatively high temperature of 420℃,Er addition suppressed grain growth.The difference in microstructure stability was then correlated with the microstructure features.Both the intermetallic phase and the solute atoms of Er inα-Mg matrix contributed to the microstructure stability.Moreover,it is believed that the existing form of Er-Zn atom pairs in theα-Mg solid solution favored the most to improve the thermal stability of the alloy.

Spatially Bandgap-Graded Mo S2（1-x）Se2x Homojunctions for Self-Powered Visible–Near-Infrared Phototransistors

Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features,which opens up new potential for device applications.Here,visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys,synthesized by a simple and controllable chemical solution deposition method,are reported.The graded bandgaps,arising from the spatial grading of Se composition and thickness within a single domain,are tuned from 1.83 to 1.73 eV,leading to the formation of a homojunction with a builtin electric field.Consequently,a strong and sensitive gate-modulated photovoltaic effect is demonstrated,enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1,a specific detectivity up to^10^11 Jones,and an on/off ratio up to^10^4.Remarkably,when illuminated by the lights ranging from 405 to 808 nm,the biased devices yield a champion photoresponsivity of 191.5 A W−1,a specific detectivity up to^1012 Jones,a photoconductive gain of 10^6–10^7,and a photoresponsive time in the order of^50 ms.These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions.

多功能二维玻璃态石墨烯器件用于可见光-近红外光探测与挥发性液体传感

本文设计了基于二维玻璃态石墨烯的多功能器件.与本征石墨烯相比,扭曲的晶格结构打开了玻璃态石墨烯的带隙,表现出与石墨烯类似甚至更优异的光电探测与化学传感性能.由于玻璃态石墨烯与空气中的小分子间较强的相互作用,该器件受到光致脱附的影响更小,呈现出正的光响应.在405 nm的激光照射下,器件的响应率为0.22 A W^(-1),探测率为10^(10)Jones.此外,玻璃态石墨烯中的固有缺陷和应变可增强分析物的吸附,获得良好的化学传感性能.玻璃态石墨烯器件探测丙酮的信噪比为48,比石墨烯器件提高了50%以上.此外,对偏压和厚度有关的挥发性有机化合物(VOC)感测功能的分析表明,少层玻璃态石墨烯更为敏感.这项研究表明玻璃态石墨烯在集成光电探测和化学传感多功能器件方面具有巨大应用前景.

Negative differential friction coefficients of two-dimensional commensurate contacts dominated by electronic phase transition

Friction force(f)usually increases with the normal load(N)macroscopically,according to the classic law of Da Vinci–Amontons(f=μN),with a positive and finite friction coefficient(μ).Herein near-zero and negative differential friction(ZNDF)coefficients are discovered in two-dimensional(2D)van der Waals(vdW)magnetic CrI_(3)commensurate contacts.It is identified that the ferromagnetic–antiferromagnetic phase transition of the interlayer couplings of the bilayer CrI_(3)can significantly reduce the interfacial sliding energy barriers and thus contribute to ZNDF.Moreover,phase transition between the in-plane(p_(x)and p_(y))and out-of-plane(p_(z))wave-functions dominates the sliding barrier evolutions,which is attributed to the delicate interplays among the interlayer vdW,electrostatic interactions,and the intralayer deformation of the CrI_(3)layers under external load.The present findings may motivate a new concept of slide-spintronics and are expected to play an instrumental role in design of novel magnetic solid lubricants applied in various spintronic nano-devices.