半波长管传声损失分析

1/4波长管和Herschel-Quincke(HQ)管具有良好消声潜力,在其固有频率附近具有很高的消声量级,为了将这种消声潜力在更小的安装空间内和更宽的频带上发挥出来,设计了一种新的半波长管,通过对多管传声损失理论模型的推导,运用数值计算的方法,分析了传声损失的影响因素并对多分支管模型进行宽频带尺寸设计,最终实现在3...     

Active sites in CO2 hydrogenation over confined VOx-Rh catalysts

Science China Chemistry - Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation, especially for the ethanol synthesis. However, this reaction usually suffers low CO2...     

Charge storage mechanisms of cathode materials in rechargeable aluminum batteries

Science China Chemistry - Rechargeable aluminum batteries (RABs) have attracted great interest as one of the most promising candidates for large-scale energy storage because of their high...     

Stereo-controlled anti-hydromagnesiation of aryl alkynes by magnesium hydrides

A concise protocol for anti-hydromagnesiation of aryl alkynes was established using 1 : 1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI₂) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH₂) is responsible for the process.

Anti-hydromagnesiation of aryl alkynes was facilitated solely by magnesium hydride. The resulting alkenylmagnesium intermediates were functionalized with various electrophiles to afford stereochemically defined tri-substituted alkenes.     

Efficient and stable Ruddlesden-Popper layered tin-based perovskite solar cells enabled by ionic liquid-bulky spacers

The crucial component, bulky spacers, in two-dimensional Ruddlesden-Popper(2 DRP) layered tin(Sn) perovskites are highly limited by halide ammonium salts, leading to the insufficient control of complex crystallization process due to the limited interaction between bulky spacers and 2 DRP perovskite frameworks. Here, we report an ionic liquid-bulky spacer, butylammounium acetate(BAAc O), for constructing efficient and stable 2 DRP Sn-based perovskite solar cells(PSCs). In contrast to the traditional halide ammonium bulky spacer, butylammounium iodide(BAI), the Ac O--functional group in BAAc O has a strong interaction with formamidine ions(FA+) and Sn2+. The inter-component interaction allows the formation of controllable intermediates for the favorable growth of smooth, dense, and highly oriented perovskite films. A PSC with power conversion efficiency of 10.36%(7.16% for BAI) is achieved, which is the highest report, along with improved stability with ～90% retained after ～600 h storage in N2 atmosphere without any encapsulation.     

间甲钴黏合体系在轮胎骨架材料中的黏合机理研究

为验证与进一步探索黏合树脂及钴盐对轮胎与镀铜钢丝帘线的增黏作用机理,选取传统黏合树脂R80与2种新型黏合树脂HT1005和H620,通过对2种新型黏合树脂的结构分析、橡胶硫化特性、静态T抽出测试与力学性能测试,并设计了一种新的黏合层强度测试方法与黏合层表征方法,进行机理探索,得出如下结论:含有羟基的极性黏合树脂在橡胶硫化时,会由于与非极性天然橡胶的极性差异产生的热力学不相容从而产生自动相分离,向橡胶与镀铜钢丝的界面层进行迁移汇集,且极性越高迁移能力越强,产生一个介于橡胶与镀铜钢丝之间的树脂富集层.因为黏合树脂交联反应温度为140℃左右,会在天然橡胶硫化反应时发生同步交联反应,黏合树脂形成的网络模量高于橡胶硫化网络,会增强镀铜钢丝与橡胶之间的黏合层强度,并形成一个镀铜钢丝与橡胶之间的模量过渡层,进一步增强黏合层.且极性越强,树脂网络交联程度与橡胶硫化网络交联程度越接近,增黏效果越好;钴盐会活化橡胶中的S,使更多的S迁移到镀铜钢丝表面从生成更多硫化亚铜键,增强黏合.     

Layered V-MOF nanorods for rechargeable aqueous zinc-ion batteries

Metal–organic frameworks (MOFs) have attracted great attention owing to their controllable morphologies, adjustable aperture, and large specific surface areas. Here, a typical V-MOF (MIL-47) product is successfully synthesized via a one-step hydrothermal method, which is explored to have a one-dimensional layered nanorod-like framework. From a microcosmic point of view, such a V-MOF product is equipped with a rhomboid structure with a large number of empty channels, which is beneficial for guest ions freely inserting in and extracting from the structure. Hence, the V-MOF product is utilized as the cathode material for the aqueous MOF-Zn battery, which exhibits a high initial specific capacity of 320 mA h/g at 0.1 A/g, and a desirable rate capability and cycling performance.     

Polycyclic naphthalenediimide-based nanoparticles for NIR-Ⅱ fluorescence imaging guided phototherapy

Optical imaging and phototherapy in the second near-infrared window(NIR-Ⅱ, 900–1700 nm) can reduce tissue auto-fluorescence and photon scattering, which facilitates higher spatial resolution and deeper tissue penetration depth for solid tumor theranostics. Herein, a polycyclic naphthalenediimide(NDI) based chromophore 13-amino-4,5-dibromo-2,7-di(dodecan-6-yl)-1 H-isoquinolino[4,5,6-fgh]naphtho[1,8-bc][1,9]phenanthroline-1,3,6,8(2H,7H,9H)-tetraone(NDI-NA) was designed and synthesized. With large polycyclic π-systems, NDI-NA molecule possesses broad near-infrared(NIR) absorption(maximum at777 nm) and emission(maximum at 921 nm). By nanoprecipitation, NDI-NA nanoparticles(NPs) were formed in aqueous solution with J-aggregative state, which showed huge red-shift in both absorption spectrum(maximum at 904 nm) and emission spectrum(maximum at 1,020 nm), endowing NDI-NA NPs efficient NIR-Ⅱ fluorescence imaging capability. Besides, the NPs present effective tumor-targeting capability in vivo based on the enhanced permeation and retention(EPR) effect. More importantly, NDI-NA NPs simultaneously have high photothermal conversion efficiency(30.8%) and efficient reactive oxygen species generation ability, making them remarkably phototoxic to cancer cells. The polycyclic chromophore based multifunctional NDI-NA NPs as NIR-Ⅱ phototheranostic agents possess bright future for clinical NIR-Ⅱ imaging-guided cancer phototherapy.     

锂硫电池隔膜功能化设计

锂硫电池具有较高的理论比容量(以硫计1675 mAh·g^-1和2600 Wh·kg^-1),以及低成本和绿色环保等优势,成为最有前景的下一代可充电储能器件之一。然而,锂硫电池内部严重的多硫化锂穿梭现象导致了电池容量的下降和使用寿命的快速降低。为实现锂硫电池的商业化,其严重的“穿梭效应”亟需改善。普通的商业隔膜有很大的孔径(500 nm),且不具有阻碍多硫化锂迁移的功能。因此,对隔膜进行表面修饰,引入功能化修饰层就成为了一种很有效的策略。本文综述了近年来隔膜表面修饰所遵循的方法以及在此基础上开发的新型隔膜,并对功能化的隔膜在提升锂硫电池性能上的前景进行了展望。     

A dynamic time-varying reliability model for linear guides considering wear degradation

Nonlinear Dynamics - This paper devotes to providing a dynamic reliability model for linear guideways for the whole life. Since a linear guide is always worn, the wear degradation of the linear...