Gas Sensing of NiO‐SCCNT Core–Shell Heterostructures: Optimization by Radial Modulation of the Hole‐Accumulation Layer

Hierarchical core–shell (C–S) heterostructures composed of a NiO shell deposited onto stacked‐cup carbon nanotubes (SCCNTs) are synthesized by atomic layer deposition (ALD). A film of NiO particles (0.80–21.8 nm in thickness) is uniformly deposited onto the inner and outer walls of the SCCNTs. The electrical resistance of the samples is found to increase of many orders of magnitude with the increasing of the NiO thickness. The response of NiO–SCCNT sensors toward low concentrations of acetone and ethanol at 200 °C is studied. The sensing mechanism is based on the modulation of the hole‐accumulation region in the NiO shell layer upon chemisorption of the reducing gas molecules. The electrical conduction mechanism is further studied by the incorporation of an Al₂O₃ dielectric layer at NiO and SCCNT interfaces. The investigations on NiO–Al₂O₃–SCCNT, Al₂O₃–SCCNT, and NiO–SCCNT coaxial heterostructures reveal that the sensing mechanism is strictly related to the NiO shell layer. The remarkable performance of the NiO–SCCNT sensors toward acetone and ethanol benefits from the conformal coating by ALD, large surface area of the SCCNTs, and the optimized p‐NiO shell layer thickness followed by the radial modulation of the space‐charge region.     

Positively Thermo‐Sensitive Monodisperse Core–Shell Microspheres

In this paper, we report on a novel family of monodisperse thermo‐sensitive core–shell hydrogel microspheres that is featured with high monodispersity and positively thermo‐responsive volume phase transition characteristics with tunable swelling kinetics, i.e., the particle swelling is induced by an increase rather than a decrease in temperature. The microspheres were fabricated in a three‐step process. In the first step, monodisperse poly(acrylamide‐co‐styrene) seeds were prepared by emulsifier‐free emulsion polymerization. In the second step, poly(acrylamide) or poly[acrylamide‐co‐(butyl methacrylate)] shells were fabricated on the microsphere seeds by free radical polymerization. In the third step, the core–shell microspheres with poly‐ (acrylamide)/poly(acrylic acid) based interpenetrating polymer network (IPN) shells were finished by a method of sequential IPN synthesis. The proposed monodisperse core–shell microspheres provide a new mode of the phase transition behavior for thermo‐sensitive “smart” or “intelligent” monodisperse micro‐actuators that is highly attractive for targeting drug delivery systems, chemical separations, sensors, and so on.     

磁引信应用中的壳体屏蔽效应分析

针对磁引信在应用中遇到的壳体屏蔽问题,提出将引信体近似为回转椭球壳体模型,从理论上详细地分析了椭球壳体在均匀磁场中的屏蔽效应,给出了相应的屏蔽系数公式;并通过试验验证了理论分析的正确性.该研究分析对磁引信体的选材、结构设计及所测得的磁信号处理都有重要的意义.     

Improvement of Biological Organisms Using Functional Material Shells

Biomineralization brings inorganic materials into biological organisms and it plays an important role in natural evolution. Inspired by biomineralized eggs and diatoms with protective shell structures, scientists have artificially endowed organisms with functional materials. The resulting organism–material hybrids become more robust and even evolve new functions. This feature article reviews recent achievements of organism improvements by various material shells and related applications in cell protection, storage, thermal stability, biological stealth, photosynthesis and biocatalysis, etc. Different from the previous understanding of biomineralization, the regulation effects of materials on organism functions are highlighted in these biomineralization‐inspired biological improvements, which present an artificial evolution strategy by using material techniques. We suggest that rationally designed organism–materials with optimized functions can shed light on solving global problems such as energy crisis and environmental pollution, as well as on improving medical treatment and intricate material designing. More generally, the studies of material‐based organism improvement can combine biological and material sciences together for a closer integration.     

铝合金薄壁圆柱壳切削稳定性研究

对于圆柱壳的加工,由工件材料的性能和结构特点,可知其相对刚度较低,加工工艺性差,易变形,在加工中易产生振动。再生型切削颤振是机床切削振动的主要原因。在现有文献的基础上研究了圆柱壳再生型切削颤振系统极限切削宽度随机床主轴转速变化的规律,并通过动态测试实验、模态实验和动态切削力实验,对切削系统的动力学参数进行识别,最终得到了圆柱壳切削系统稳定性极限图,并在传统稳定性的基础上提出严格稳定区的概念。     

精密外罩的成形工艺及模具

分析了外罩的工艺性能和材料性能,叙述了精密外罩的成形工艺及其模具结构.     

用倒计时法实现一定时间间隔的测量

针对被检交流稳压电源输出频率稳定度测试,即测试输出频率随时间的变化情况,本文充分开发和利用LabVIEW 8.5开发环境中已用时间函数,采用倒计时显示剩余时间的方法,设计了实现任意设置时间间隔内,对同一被测对象进行多次测量、数据处理、存盘的程序.该程序简单实用,提高了检定系统的自动化程度,对使用者带来极大的方便,具有较高的应用、借鉴价值.     

动态云雾形成及爆轰场特性

为获得动态云雾爆轰的超压场分布特征,采用空投方法实现动态云雾的形成和爆轰过程。利用高速运动分析系统和压力测试系统分别对动态云雾分散、爆轰过程和动态爆轰超压场进行测量,对动态云雾的燃料抛撒和超压场分布进行了研究,分析了轴向有加强杆装置结构和轴向无加强装置杆结构对动态云雾爆轰超压场的影响规律。结果表明:轴向无加强杆结构和轴向有加强杆结构的动态最大峰值超压分别为3.62 MPa和3.20 MPa,轴向无加强杆结构具有较大的毁伤距离;动态爆轰最大峰值超压较静态爆轰最大峰值超压提高31.2%,且动态爆轰毁伤距离大于静态爆轰。     

Metal–Organic Frameworks Derived from Zero‐Valent Metal Substrates: Mechanisms of Formation and Modulation of Properties

The replicative construction of metal–organic frameworks (MOFs) templated with solvent‐insoluble solid substrates is of marked importance, as it allows for the assembly of 2D and 3D macro‐ and mesoscopic architectures with properties that are challenging to attain by the conventional solution‐based synthesis approach. This work reports an in situ and direct construction of MOFs from zero‐valent metal substrates via a green hydrothermal oxidation–MOF construction chemistry without the use of any additional metal source, chemical reagents, or acidification of solvent, and elucidates the zero‐valent metal derived formation mechanisms of MOFs and their structure modulation to 1D nanofibers (NFs), 2D film, and 3D core–shell microstructures. Through modulation of the competing surface oxidation‐dissolution and MOF crystallization kinetics, Al@MIL‐53 core–shell microstructures and MIL‐53 (Al) NFs are obtained that exhibit unique morphologies and marked properties superior to the conventional MIL‐53 (Al) powders. The generality of zero‐valent metal‐templated synthesis of MOFs is demonstrated with formation of MIL‐53 (Al), HKUST‐1, and ZIF‐7 polycrystalline films on Al, Cu, and Zn metal meshes, elucidating the significance of the approach utilizing solid metal substrate that can be easily processed into various shapes, architectures, and compositions.