Co‐development of Crystalline and Mesoscopic Order in Mesostructured Zeolite Nanosheets

Mesoporous zeolites are a new and technologically important class of materials that exhibit improved diffusion and catalytic reaction properties compared to conventional zeolites with sub‐nanometer pore dimensions. During their syntheses, the transient developments of crystalline and mesoscopic order are closely coupled and challenging to control. Correlated solid‐state NMR, X‐ray, and electron microscopy analyses yield new molecular‐level insights on the interactions and distributions of complicated organic structure‐directing agents with respect to crystallizing zeolite frameworks. The analyses reveal the formation of an intermediate layered silicate phase, which subsequently transforms into zeolite nanosheets with uniform nano‐ and mesoscale porosities. Such materials result from coupled surfactant self‐assembly and inorganic crystallization processes, the interplay between which governs the onset and development of framework structural order on different length and time scales.     

Nickel‐Rich Layered Lithium Transition‐Metal Oxide for High‐Energy Lithium‐Ion Batteries

High energy‐density lithium‐ion batteries are in demand for portable electronic devices and electrical vehicles. Since the energy density of the batteries relies heavily on the cathode material used, major research efforts have been made to develop alternative cathode materials with a higher degree of lithium utilization and specific energy density. In particular, layered, Ni‐rich, lithium transition‐metal oxides can deliver higher capacity at lower cost than the conventional LiCoO₂. However, for these Ni‐rich compounds there are still several problems associated with their cycle life, thermal stability, and safety. Herein the performance enhancement of Ni‐rich cathode materials through structure tuning or interface engineering is summarized. The underlying mechanisms and remaining challenges will also be discussed.     

Encapsulation of Functional Organic Compounds in Nanoglass for Optically Anisotropic Coatings

A novel approach is presented for the encapsulation of organic functional molecules between two sheets of 1 nm thin silicate layers, which like glass are transparent and chemically stable. An ordered heterostructure with organic interlayers strictly alternating with osmotically swelling sodium interlayers can be spontaneously delaminated into double stacks with the organic interlayers sandwiched between two silicate layers. The double stacks show high aspect ratios of >1000 (typical lateral extension 5000 nm, thickness 4.5 nm). This newly developed technique can be used to mask hydrophobic functional molecules and render them completely dispersible in water. The combination of the structural anisotropy of the silicate layers and a preferred orientation of molecules confined in the interlayer space allows polymer nanocomposite films to be cast with a well‐defined orientation of the encapsulated molecules, thus rendering the optical properties of the nanocoatings anisotropic.     

Synthesis of Inorganic Structural Isomers By Diffusion‐Constrained Self‐Assembly of Designed Precursors: A Novel Type of Isomerism

The structure of precursors is used to control the formation of six possible structural isomers that contain four structural units of PbSe and four structural units of NbSe₂: [(PbSe)_1.14]₄[NbSe₂]₄, [(PbSe)_1.14]₃[NbSe₂]₃[(PbSe)_1.14]₁[NbSe₂]₁, [(PbSe)_1.14]₃[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₂, [(PbSe)_1.14]₂[NbSe₂]₃[(PbSe)_1.14]₂[NbSe₂]₁, [(PbSe)_1.14]₂[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₁[(PbSe)_1.14]₁[NbSe₂]₁, [(PbSe)_1.14]₂[NbSe₂]₁[(PbSe)_1.14]₁[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₁. The electrical properties of these compounds vary with the nanoarchitecture. For each pair of constituents, over 20 000 new compounds, each with a specific nanoarchitecture, are possible with the number of structural units equal to 10 or less. This provides opportunities to systematically correlate structure with properties and hence optimize performance.     

Synthesis of Carbon/Sulfur Nanolaminates by Electrochemical Extraction of Titanium from Ti2SC

Herein we electrochemically and selectively extract Ti from the MAX phase Ti₂SC to form carbon/sulfur (C/S) nanolaminates at room temperature. The products are composed of multi‐layers of C/S flakes, with predominantly amorphous and some graphene‐like structures. Covalent bonding between C and S is observed in the nanolaminates, which render the latter promising candidates as electrode materials for Li‐S batteries. We also show that it is possible to extract Ti from other MAX phases, such as Ti₃AlC₂ , Ti₃SnC₂ , and Ti₂GeC, suggesting that electrochemical etching can be a powerful method to selectively extract the “M” elements from the MAX phases, to produce “AX” layered structures, that cannot be made otherwise. The latter hold promise for a variety of applications, such as energy storage, catalysis, etc.     

Self‐Pillared,Single‐Unit‐Cell Sn‐MFI Zeolite Nanosheets and Their Use for Glucose and Lactose Isomerization

Single‐unit‐cell Sn‐MFI, with the detectable Sn uniformly distributed and exclusively located at framework sites, is reported for the first time. The direct, single‐step, synthesis is based on repetitive branching caused by rotational intergrowths of single‐unit‐cell lamellae. The self‐pillared, meso‐ and microporous zeolite is an active and selective catalyst for sugar isomerization. High yields for the conversion of glucose into fructose and lactose to lactulose are demonstrated.     

双驱动激波管稀疏波破膜技术研究

本文介绍了在双驱动激波管中运用稀疏波破膜的技术。在以压缩空气和氮气作实验气体的情形下,实验研究了中间段长度、稀疏波强度及中间段B膜的破膜压力（压差）对第二激波追韩第一激波的影响。实验结果表明：中间段的长短,显著地制约着前后两道激波的间隔;稀疏波强度及中间段B膜的破膜压力对稀疏波破膜时间及第二激小对反射稀疏波的追赶有重要影响。     

双周期裂纹压电材料反平面剪切问题断裂力学分析

研究压电材料双周期裂纹反平面剪切与平面电场作用的问题．运用复变函数方法，获得了该问题严格的闭合解，并由此给出了裂纹尖端应力强度因子和电位移强度因子的精确公式．数值算例显示了裂纹分布特征对材料断裂行为的重要影响．叠间小裂纹能够对主裂纹的应力和电位移场起着屏蔽作用，相反行间小裂纹却起着放大作用，至于钻石形分布裂纹的影响规律则更为复杂．对于某些特殊情形给予了解答并导出一系列有意义的结果。     

一种新的运动激波--非定常边界层相互干扰现象

本文探讨了一种新的激波－非定常边界层相互干扰现象，这种激波－边界层干扰现象既不同于定常激波－边界层干扰现象，又不同于激波在端面反射后与该激波所诱导的边界层之间的干扰现象，而是运动激波与稀疏波和第一激波所诱导的非这常边界层之间的干扰现象，本文对这种现象用微波动力学理论进行分析，并把这种干扰现象看成激波的绕射现象，同时在稀疏波破膜的双驱动激波管中进行实验观察，最后把理论分析与实验观察进行了比较。     

The Effects of Blowing and Suction on Double Diffusion by Mixed Convection over Inclined Permeable Surfaces

A boundary layer analysis is used to investigate the effect of lateral mass flux on mixed convection heat and mass transfer over inclined permeable surfaces in porous media. The conservation equations that govern the problem are reduced to a system of non-linear ordinary differential equations and then the resulting equations is solved by numerical method. The numerical results for heat and mass transfer in terms of Nusselt and Sherwood number are presented in x-y plots for the buoyancy ratio (N) and Lewis number (Le) with mass flux pammeter (Fw). The obtained results are validated against previously published results with on special case of the problem.