关键词： 磺化碳纳米粉   二硫化钨   载流磨损率   抗磨性  

摘要： 为探究磺化碳纳米粉(SCN)和二硫化钨(WS2) 2种添加剂对树脂基炭刷材料抗磨性能的影响,以鳞片石墨粉为导电填料,环氧树脂为黏结剂,采用树脂分散添加剂,经混捏、破碎、冷压成型、固化等工艺制得树脂基炭刷材料,并对其进行性能测试。研究表明,在相同的载流磨损测试条件下,磺化碳纳米粉改性的炭刷材料平均载流磨损率为2.5 mg/h,相较于未加入添加剂的炭刷,其抗磨性能提升了67.7%;WS2改性的炭刷平均载流磨损率为3.35 mg/h,相较于未加入添加剂的炭刷,其抗磨性能提升了56.8%。经碳纳米粉和WS2改性的环氧树脂基炭刷材料其微观结构和抗磨性能均得到了显著改善,具体作用机制可推测是磺化碳纳米粉为力学增强型抗磨作用机制,WS2为减摩润滑型抗磨作用机制。

关键词： 材料表面微结构   循环肿瘤细胞   粘附和增殖   捕获率  

摘要： 目的探讨不同材料界面微观结构对循环肿瘤细胞(CTC)粘附、增殖及捕获率的影响。方法采用真空辅助软压印、水热法制备微米结构、纳米结构、微纳结构TiO2基底,连同氟掺杂氧化锡(FTO)玻璃共4种基底,修饰上皮细胞黏附分子抗体(anti-EpCAM)后进行人乳腺癌细胞系MCF-7和人宫颈癌细胞Hela的捕获实验,扫描电镜观察捕获细胞的形貌特征,荧光显微镜分析细胞增殖情况及捕获率。结果在微纳结构中,微米柱与纳米线在促进细胞粘附和铺展上具有协同作用,当微米柱间距合适时,细胞呈扁平状完全摊开。在捕获细胞孵育24 h后,微纳结构表面的细胞呈现明显增殖,细胞密度最大,单位面积细胞数为170个,明显多于其他3种结构界面(P<0.01)。随着孵育时间(30~60min)的延长,4种结构表面的捕获细胞逐渐增多(P<0.01),60 min后细胞捕获率基本不再增加;孵育60 min时,微纳结构的细胞捕获率最高,光滑表面则最低(P<0.01),且4种结构对Hela的捕获率均显著低于MCF-7(P<0.01)。结论相对于光滑表面、微米和纳米结构表面,仿荷叶微纳结构表面最有利于CTC粘附、铺展和增殖,具有最高的细胞捕获率。

关键词： 纳米银   纳米氧化锌   双眉虫   细胞毒性   超微结构  

摘要： 本文利用光学显微镜、电子显微镜技术研究了30 nm粒径圆球形纳米银颗粒及30 nm粒径圆球形纳米氧化锌颗粒对双眉虫(Diophrys sp.)细胞超微结构的影响.结果显示,这两种纳米材料均对细胞结构造成了一些相似的影响,主要表现在:(1)细胞内形成大量空泡;(2)线粒体出现肿胀、内部嵴断裂以及局部结构模糊和变空的现象;(3)细胞内出现大量自噬体,以及自噬后形成的髓鞘样小体.此外,纳米银颗粒处理组还出现细胞核核仁消失,核膜界限模糊的现象;纳米氧化锌处理组还发生了纤毛杆处质膜融合,细胞中产生大量溶酶体的现象.初步推测,纳米银颗粒主要通过影响细胞核功能,进而造成其他生命活动紊乱,而纳米氧化锌颗粒则会诱导细胞凋亡和破坏纤毛器结构从而限制细胞运动.

关键词： coexisting nanophases   lead-free piezoelectrics   phase boundary engineering   polarization rotation  

摘要： Piezoelectric materials interconvert between electrical energy and mechanical strain and are widely used for electronic and electromechanical devices. Owing to growing environmental concerns, development of lead-free piezoelectric materials with enhanced properties becomes of great interest. Key to the academic problem is a lack of fundamental understanding on the actual mechanisms involved at the microscopic (unit cell) level. While it is well known that giant responses occur near structural phase boundaries, and it has long been proposed that polarization rotation and nanodomains are major determinants, so far, atomistic understanding of the origin of the response has come mostly from theoretical simulations. Recently, notable breakthroughs have been achieved in improving the properties of piezoceramics and thin films. Precise mapping of atomic displacements by atomically resolved Z-contrast imaging has demonstrated that gradual polarization rotation bridges the coexisting nanophases. These structural features, which take place on a length scale of just a few nanometers, now visible through aberration-corrected microscopy, provide a new pivotal understanding on the outstanding piezoelectric behavior that has been obtained in all systems. They also provide key guiding principles for the development of lead-free piezoelectrics, especially in the form of thin films, which remain far behind bulk ceramics at the time being. Coexistence of nanophases with flexible interconversion, introduced via phase boundary engineering, holds much promise for achieving high performance in other material systems with phase transitions.

关键词： alkali activated   blast furnace slags   microstructure   mechanical properties  

摘要： This paper investigated the effect of blast furnace slags (BFS) characteristics on the properties achievement after being alkali activated. The physical and chemical characteristics of BFS were determined by X-ray fluorescence (XRF), X-ray Diffraction (XRD) and laser granulometry. Multi-technical characterizations using calorimetry, XRD, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG-DTG), scanning electron microscope (SEM), nitrogen sorption and uniaxial compressive strength (UCS) were applied to give an in-depth understanding of the relationship between the reaction products, microstructure and BFS characteristics. The test results show that the microstructure and mechanical properties of alkali activated blast furnace slags (BFS) highly depend on the characteristics of BFS. Although the higher content of basic oxide could accelerate the hydration process and result in higher mechanical properties, a poor thermal stabilization was observed. On the other hand, with a higher content of Fe, the hydration process in alkali activated BFS2 lasts for a longer time, contributing to a delayed compressive strength achievement.

关键词： 共晶炸药   微结构设计   制备方法  

摘要： 共晶炸药具有较好的爆热、更高的氧平衡、更低的感度以及更高的安全性。共晶技术可有效改善单质炸药的不足之处,扩大其应用范围。综述了共晶炸药的微结构设计、模拟及制备方法,进一步评价了不同制备方法的特点,总结了共晶炸药发展现状,并对未来共晶炸药的研究方向进行了展望。

关键词： Composite phase change material   Carbonate salts   Thermal energy storage   Microstructures   Thermal cycling   Salt migration  

摘要： We investigated the microstructures and their formation mechanisms of carbonate salt based composite phase change materials (CPCMs). Such materials typically consist of a carbonate salt as the phase change material (PCM), a thermal conductivity enhancement material (TCEM) and a ceramic skeleton material (CSM) for structure stabilisation, and are mainly for medium and high temperature thermal energy storage applications. Two carbonate salt based composites were studied with one being eutectic NaLiCO3 and the other Na2CO3. MgO and graphite flakes were used respectively as the CSM and TCEM for fabricating the composite modules. A scanning electron microscope with energy dispersive spectrometer (SEM-EDS) was used to observe the microstructures and the salt distribution and redistribution within the composite structures during repeated melting-solidification cycles. The results showed salt migration within the composite structure during the thermal cycling. Such a microscopic motion led to a more homogenous distribution of not only the salt but also the CSM and TCEM. At a low graphite flake loading, breakage of the graphite flake was observed, suggesting stress generation during thermal cycling. The extent of the breakage reduced with increasing graphite flake loading, suggesting the stress generation be related to microscopic motion. The MgO based CSM particles were likely to be sintered, forming a porous structure. Such a structure reduced the swelling effect partially due to the use of graphite on which the salts had a poor wettability.

关键词： 纳米金刚石薄膜   硫离子注入   电化学性能   微结构  

摘要： 采用热丝化学气相沉积法制备纳米金刚石薄膜,并对薄膜进行硫离子注入和真空退火处理.系统研究了退火温度对薄膜微结构和电化学性能的影响.结果表明,硫离子注入有利于提升薄膜的电化学可逆性.在800°C及以下温度退火时,薄膜中晶界处的非晶碳相逐渐向反式聚乙炔相转变,致使电化学性能逐渐变差.当退火温度上升到900°C时, Raman光谱和TEM结果显示此时薄膜中金刚石相含量较多且晶格质量较好,晶界中的反式聚乙炔发生裂解;X射线光电子能谱结果表明,此时C-O键、C=O键、p-p*含量显著增多;Hall效应测试显示此时薄膜迁移率与载流子浓度较未退火时明显升高;在铁氰化钾电解液中氧化还原峰高度对称,峰电位差减小至0.20 V,电化学活性面积增加到0.64 mC/cm^2,电化学可逆性远好于600, 700, 800°C退火时的样品.

关键词： Grain boundary   Boundary element method   Microstructural modelling   Polycrystalline materials   Multilayer actuator  

摘要： A two-dimensional grain boundary formulation is presented for the micromechanical analysis of multilayer barium titanate ceramics. A boundary element formulation of the elastic problem is generated for single grains of the polycrystalline, as well as for heterogeneous aggregation and the assumption of traction equilibrium and displacement compatibility. In order to obtain the microstructural model of homogeneous and multilayer actuator, the solid-state technique is applied for the preparation of BaTiO3powder. Image-processing technique is employed in order to discretize the grains boundaries but not their surface, resulting in the significant simplification of data preparation. The integrity of the collection is guaranteed by applying both continuity and equilibrium at the interface between contiguous grains. The numerical homogenization of the 2D polycrystals is performed by the developed technique, and a comparison with the available data is presented.

关键词： AC impedance spectroscopy   Equivalent circuit model   Hydration   Microstructure   Chloride induced corrosion  

摘要： As a non-destructive method, AC impedance spectroscopy is a promising technique for the characterization of cement-based materials owing to its advantages in real time monitoring. In this paper, the equivalent circuit models in publications applied for different cement-based systems are summarized. The determinations of hydration properties, microstructural changes and chloride induced corrosion parameters of cement-based materials by AC impedance spectroscopy measurements are reviewed. With some appropriate models, the AC impedance parameters can be applied to characterize microstructure and interfacial properties of cement-based materials. The experimental condition control and data analyses are discussed. Some improvements for measurement device and development of equivalent circuit models for different kinds of binding materials are needed.