关键词： 电沉积条件   纳米晶镍   晶粒尺寸   择优取向  

摘要： 电沉积金属镀层的微观结构对镀层性能有重要影响,而镀层微观结构与电沉积条件密切相关。通过电沉积法制备了具有择优取向的纳米晶镍镀层,研究了电流密度、电沉积时间、表面活性剂浓度、镀液温度等电沉积条件对镍镀层平均晶粒尺寸和晶面择优取向的影响,分析和讨论了镀层显微硬度随晶粒尺寸和晶面择优取向变化的机理。结果表明:纳米晶镍镀层的晶粒尺寸与晶面择优取向可通过改变电沉积条件进行调控,不同沉积条件下得到的纳米晶镍镀层平均晶粒尺寸在6~35 nm范围内,镍纳米晶择优取向主要在(111)和(200)晶面变化;晶粒尺寸和晶面择优取向共同影响纳米晶镍镀层的显微硬度。

关键词： 纳米载体   微观结构   控释性能   “构-性”关系  

摘要： 本文探讨纳米载体微观结构变化的影响因素,以及随着微结构的改变,载体宏观性状和载药释药性能变化,旨在阐述药物载体的"结构-性能"的相关性。

关键词： Fusion materials   Ductile-phase toughening   Damage modeling   Multiscale analysis   Crack propagation   Finite element  

摘要： Increasing fracture toughness and modifying the ductile-brittle transition temperature of a tungsten-alloy relative to pure tungsten has been shown to be feasible by ductile-phase toughening (DPT) of tungsten for future plasma-facing materials for fusion energy. In DPT, a ductile phase is included in a brittle tungsten matrix to increase the overall work of fracture for the material. This research models the deformation behavior of DPT tungsten materials, such as tungsten-copper composites, using a multiscale modeling approach that involves a microstructural dual-phase (copper-tungsten) region of interest where the constituent phases are finely discretized and are described by a continuum damage mechanics model. Large deformation, damage, and fracture are allowed to occur and are modeled in this region that is connected to adjacent homogenized elastic regions to form a macroscopic structure, such as a test specimen. The present paper illustrates this multiscale modeling approach to analyze unnotched and single-edge notched (SENB) tungsten-copper composite specimens subjected to three-point bending. The predicted load-displacement responses and crack propagation patterns are compared to the corresponding experimental results to validate the model. Such models may help design future DPT composite configurations for fusion materials, including volume fractions of ductile phase and microstructural optimization. (C) 2018 Published by Elsevier B.V.

关键词： Polymer composites   tidal turbine blade   water aging   X-ray computed tomography   ocean energy   manufacturing defects   composite voids  

摘要： The lifespan and economic viability of tidal energy devices are constrained, in part, by the complex degradation of the tidal turbine blade materials due to prolonged immersion in a hostile sub-sea environment. Seawater penetration is a significant degradation mechanism in composite materials. This work aims to investigate the influence of microstructure and hydrostatic pressure on water absorption in four polymer composites which are candidate materials for use in tidal energy devices. These materials are: a glass fibre powder epoxy, a carbon fibre powder epoxy, glass fibre Ampreg epoxy and a chopped fibre glass fibre Polyether Ether Ketone. X-ray computed tomography is used to characterise the voids, resin-rich areas and other manufacturing defects present in each material. These defects are known to significantly alter the rate of moisture diffusion, as well as the total uptake of water at saturation. The samples are then exposed to accelerated water aging and hydrostatic pressurisation in order to simulate a range of expected sub-sea operating conditions. The material micro-structure, the matrix material and pressurisation level are shown to strongly influence both the moisture absorption rate and total water uptake. Significant volumetric changes are also noted for all samples, both during and after aging. X-ray computed tomography scans of specimens also provide a unique insight into the role of voids in storing water once a material has reached saturation.

关键词： Gd and Al co-doped LiMn2O4   Li-ion battery   Improved discharge capacity   Li+ intercalation and de-intercalation   Cubic spinel structure  

摘要： Gd and Al co-doped LiMn2-x(GdAl)(x)O-4 (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) materials with spinel structure were synthesized by sol-gel method. Powder X-ray diffraction results confirm the formation of cubic spinel structure and average particle sizes are found to be between 80 and 110 nm from FE-SEM and TEM analysis. Decrease in peak potential difference as a function of doping in Cyclic Voltammetry results establishes enhancement in Li+ intercalation and de-intercalation. Electrochemical Impedance Spectroscopy (EIS) results showed that accumulation of charges on electrode has improved with doping over pristine samples. At a doping of x = 0.02 charge transfer resistance values were found to be least. First cycle charge-discharge profiles for LiMn1.96(GdAl)(0.02)O-4 shows 139.2 mAh/g discharge capacity over other doped derivatives and pure LiMn2O4 (119.6 inAh/g) in aqueous Li2SO4 electrolyte. Doping of x = 0.02 exhibit good cycling performance with only a total 4% capacity loss after 30 cycles.

关键词： Microstructural topology optimization   Viscoelastic material   Damped structure   Homogenization   Transient response  

摘要： This paper presents microstructural topology optimization of viscoelastic materials for damped structures. The microstructure is composed of periodic unit cells. The effective modulus of the viscoelastic material is obtained through the homogenization method. The density-based topology optimization is adopted to find optimal microstructures of viscoelastic materials. The design objective is to effectively attenuate transient responses of damped structures. Transient responses are evaluated with an implicit time integration scheme based on the two-scale analysis. An adjoint sensitivity analysis is developed for computation of the derivatives of transient responses of macrostructures with respect to microstructural design variables. Several numerical examples demonstrate the effectiveness of the proposed approach. Various microstructures of viscoelastic materials are presented, and their corresponding transient responses of the damped structures are discussed. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Spectroscopy   Doppler effect   Magnetism   Microstructural properties  

摘要： A large spectrum of ferritic steels with parametric variation of alloying elements were developed at EC - JRC Petten (the Netherlands) in order to understand the role and influence of Ni, Si, Cr and Mo as alloying elements and certain impurities as Cu and P on the properties of steels during irradiation. They were investigated by various non-destructive techniques in the in view of identifying the possible influence of alloying elements on material properties. In the present study we compare results of Doppler broadening annihilation spectroscopy and magnetic Barkhausen noise obtained on as-received specimens.

关键词： 原位   莫来石质材料   粉煤灰漂珠与氢氧化铝质量比   显微结构  

摘要： 以固体废弃物粉煤灰漂珠(FAFB)和工业氢氧化铝为主要原料,并添加AlF_3和V_2O_5作为矿化剂,采用原位生长法合成了莫来石质材料,研究了粉煤灰漂珠和氢氧化铝质量配比对材料的显微结构及其性能的影响。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对材料的晶相和显微结构进行了表征。实验结果表明,当粉煤灰漂珠与氢氧化铝的质量比为25∶75时,样品是由棒状的莫来石相和片状的刚玉相组成,当质量比从35∶65变化到55∶45时,可以获得针状的纯莫来石质空心球材料,且在该配方组成范围内合成的莫来石材料具有优良的性能,高的抗压强度7.6~10.5 MPa,低的体积密度0.48~0.66 g/cm3,当质量比达到65∶35时,伴随有石英相的产生。

关键词： 纳米多晶金刚石   微结构   压痕   塑性形变机制  

摘要： 纳米多晶金刚石是指晶粒尺寸小于100nm的金刚石晶粒直接结合而形成的多晶材料。石墨经高温高压直接转变合成的纳米多晶金刚石的硬度达120~145GPa,洋葱碳直接转变合成的金刚石晶粒内含高密度孪晶,此纳米孪晶金刚石硬度达200GPa,远超单晶金刚石的硬度。材料优良的性能源于其微观结构,揭示其塑性形变机制将利于更高性能纳米超硬材料的设计与合成。本文概述了纳米多晶金刚石微观结构及其塑性形变机制的国内外研究现状,重点介绍和评价了纳米多晶金刚石塑性形变机制的实验及理论研究,为纳米多晶金刚石材料的进一步研究和应用提供参考。