微孔聚合物皮层厚度测量的扫描声显微方法

微孔发泡是一种有广泛应用前景的聚合物改性方法.皮层的存在对微孔结构材料的性能有很大的影响,皮层厚度的测量、工艺控制和理论计算是微孔材料加工中的主要问题.文章介绍了一种测量微孔聚合物皮层厚度的新的有效方法--扫描声显微(SAM)方法,并测量了微孔聚苯乙烯和微孔聚碳酸酯的皮层厚度.     

微孔发泡聚合物泡孔形貌控制的研究进展

使用超临界流体技术制备微孔发泡聚合物,泡孔形貌是影响微孔聚合物性能的关键因素。针对微孔发泡聚合物泡孔形貌控制,即增加泡孔密度、减小泡孔直径、均化泡孔尺寸分布,从工艺条件、基体性质、共混改性、纳米添加剂、外加力场等影响因素出发,综述了近年来微孔发泡聚合物泡孔形貌控制的研究进展;最后展望了微孔发泡聚合物的前景。     

用于锂离子电池的四嗪环连接的共轭微孔聚合物电极性能研究

共轭微孔聚合物因其交联多孔的骨架及高度共轭的结构,在锂离子电池电极材料领域具有巨大的应用前景。以四嗪作为连接单元,构筑了具有氧化还原活性的共轭微孔聚合物TZF和TBFZ,并对该共轭微孔聚合物作为锂离子电池负极材料的性能进行了测试。结果表明,由于具有更丰富的活性单元四嗪环以及更低的最低未占分子轨道能级,TZF展现出比TBFZ更好的电化学性能。此外,在不同的电流密度下循环后,TZF比容量均有不同程度的提高。当电流密度为0.1C时,循环250次后比充电容量从62增加到108.6 mAh·g^-1;电流密度为1.0C时,循环1000次后比充电容量从40提高到139 mAh·g^-1,并且库伦效率始终接近100%,表明TZF作为锂离子电池负极材料具有良好的氧化还原活性及循环稳定性。     

扫描电子声显微镜对骨组织的成像

1引言自1980年由Brandis和Rosencwaig以及Cargill分别建立扫描电子声显微镜(SEAM)以来,由于它可以高分辨率[1]地同时获得试样表面电子显微镜像(SEM)和亚表面SEAM像以及试样制备简     

开孔型聚合物发泡材料的研究及应用进展EI北大核心CSCD

聚合物泡沫塑料以其优异的性能成为人们生活中必不可少的物品。开孔型聚合物发泡材料因独特的三维骨架形态被广泛应用于吸音材料、生物医药材料、光学材料和导电材料等领域。特别是聚合物纳米复合材料,为现代医学生产抗菌治疗、组织工程、癌症治疗、医学成像、牙科应用、药物传递等产品提供了新的机遇。本文综述了开孔发泡材料的制备方法、发泡机理及其应用领域,以及最近几年开孔发泡材料新的发展。最后,对材料制备和应用过程中存在的主要问题进行总结并对未来采用聚合物共混、形成微纳米复合材料、涂覆高阻隔材料和聚合物改性等手段制备高性能开孔聚合物发泡材料的发展趋势进行展望。     

扫描近场光学显微技术在半导体材料表征领域应用的研究进展

半导体材料及其光电器件如激光器、探测器以及高速微波器件有着广阔的应用前景。半导体材料的结构和缺陷特性对器件性能起着至关重要的影响,然而对材料进行纳米尺度下的检测、表征无论是理论上还是技术和设备上都需要深入研究和发展,因此扫描近场光学显微技术在半导体材料表征领域有着无可替代的地位。扫描近场光学显微技术突破了传统光学显微技术的衍射分辨率极限的限制,具有超高空间分辨率、超高探测灵敏度等特点,并且是一种非接触性探测,具有无损伤性。简要介绍了扫描近场光学显微镜的原理及在半导体材料研究中的应用,包括量子阱结构中的位错及缺陷的表征,半导体器件的表面复合速率及扩散长度的纳米表征,以及半导体薄膜中的缺陷分布的检测。探讨了目前相关研究领域存在的主要问题,并对其发展趋势和前景进行了展望。     

绝缘层厚度与芯线直径测量偏离方法的比对

本文探讨了绝缘层厚度与芯线直径测量装置的选择问题.通过采用不同的测量方法进行比对实验,证明只要用满足标准规定精度的测量仪器去测量,就能达到要求,并不一定要用读数显微镜,标准中方法是可以偏离的.     

绝缘层厚度与芯线直径测量偏离方法的比对

本文探讨了绝缘层厚度与芯线直径测量装置的选择问题。通过采用不同的测量方法进行比对实验,证明只要用满足标准规定精度的测量仪器去测量,就能达到要求,并不一定要用读数显微镜,标准中方法是可以偏离的。     

用两种四探针方法测量硅单晶片边缘电阻率及其结果的比较

本文简述了两种四探针方法测量硅单晶样片边缘电阻率的优缺点，及测量结果的比较，突出了双电测四探针方法的测量优点。     

基于显微CT的泥岩单轴压缩破坏特征的声发射表征

研制了基于实时声发射采集和实时加载CT扫描同步进行的加载控制系统,组建了对岩石损伤、破坏过程进行声发射表征的实验系统和实验方法。研究表明:①在峰值载荷28%前,原生裂纹宽度基本无变化,而后经历先变窄再变宽的过程。在峰值载荷47%前,原生裂纹长度基本无变化,而后开始增长,原生裂纹在宽度上先进行扩展从而引起原生裂纹在长度上的增长;②在峰值载荷65%前,裂纹的延伸发生在裂纹尖端的软弱介质中,而后才是真正的原生裂纹起裂,并快速延伸扩展;③新生裂纹易产生在软硬夹层交界处,新生裂纹产生时的载荷约为峰值载荷的56%～75%,在峰值载荷84%前,裂纹处于稳定扩展阶段,三条裂纹同时各自发展;④裂纹宽度变大、原生裂纹在其尖端软弱介质中延伸、软硬交界处新生裂纹的产生过程中声发射较少,当这些过程连在一起时,便形成了声发射平静期;⑤建立了岩石孔隙率、裂纹长度和宽度与声发射能量、振铃计数之间的表征方程,并提出不同加载阶段岩石状态评价的判据。     

层析扫描声学显微镜相关算法及其比较

为了获得物体内部清晰的三维图像,提高激光扫描声学显微镜的分辨能力,在激光扫描声学显微镜原理的基础上,阐述了层析扫描声学显微镜的结构和工作方式。结合层析技术并且根据超声波在介质中的传播规律介绍了三种层析算法:频域内的插值算法;往返传播算法;滤波反向传播算法。最后通过理论和实验比较,结果表明:往返传播算法通过对滤波函数进行改进,在有限孔径的前提下,应用于层析扫描声学显微镜时比其它两种算法可以获得更好的重建图像效果。     

Analysis of the effect of structural defects on the fatigue strength of RFSSW joints using C‐scan scanning acoustic microscopy and SEM

Solid‐state refill friction stir spot welding (RFSSW) technology offers significant benefits in the fabrication of aluminium structures in the transport and aerospace industries. In this paper, the joining of 1.6‐mm‐thick Alclad 7075‐T6 aluminium alloy sheets is investigated. High‐cycle fatigue strength tests of single‐lap welded joints were carried out on an Instron E10000 testing machine with a limited number of cycles equal to 2 × 10⁶. The welding of overlap fatigue specimens was conducted using an RPS100 spot welder by Harms & Wende GmbH & Co KG. C‐mode scanning acoustic microscopy (C‐SAM) and scanning electron microscopy (SEM) were utilised to evaluate the joint quality and characterise the microstructure. The paper discusses the effect of the maximum load force and defects (voids, hook, kissing bond, bonding ligament, etc) associated with the material flow in the weld on the failure mechanism. Insufficient plasticisation of sheet material and mixing of the material in the weld area are crucial defects that influence the number of destructive cycles. The weld defects in the joint structure are a source of a decrease in the fatigue life compared with the fatigue life of defect‐free welds. It was also found that RFSSW joint defects can be effectively detected by the nondestructive C‐SAM method.     

导电化方法对连续泡沫镍性能的影响

通过测定抗拉强度、延伸率、厚度分布系数和面密度分布等参数,对比研究了改进的浸涂导电胶、磁控溅射镍和化学镀镍等不同导电化方法对连续泡沫镍的性能的影响.结果表明:磁控溅射镍、化学镀镍和改进的导电胶法,都可制出性能优异的连续泡沫镍;在瓦特镍溶液中,研究了上述3种导电基体上镍的沉积行为,发现石墨导电胶基体上镍的还原存在明显的欠电位沉积现象.     

Meso-structures evolution rules of coal fracture with the computerized tomography scanning method

In order to observe the meso-structure and fracture process of coal interior, the computerized tomography (CT) scanning experimental system was developed. This system includes the nonmetal cylinder shell, loading head, strain test equipment, hydraulic pump and vacuum pump, which can scan coal or rock samples with or without gas under uniaxial and triaxial load. The uniaxial compression experiments of coal were done and CT images were obtained at different stress level. The results show that the raw coal is a kind of heterogeneous material and the internal distribution of density is inhomogeneous. The cracks are uneven and their directions are random. During the loading process the inner structures of coal changed. The density of the coal increases at the beginning of load and decreases with the increment of stress. The fractures of coal occur mainly between the skeleton and matrix and on the weak region of the skeleton. Moreover, CT images from the experiments were used to reconstruct 3D images of coal under different stress states. The deformation and fracture process can be observed obviously. These investigations can provide theoretical foundations for understanding of fracture mechanism of coal.     

利用电磁超声横波检测二冷区尾端连铸坯壳厚度

使用电磁超声横波对二冷区尾端的连铸坯壳厚度进行检测,并建立了有限元仿真模型.选取Q235连铸小钢坯作为被测对象.为减小永磁铁的提离距离、在被测体内部生成更大的感应涡流,文章利用多物理场有限元仿真软件建立了一种不同于一般结构的电磁超声换能器仿真模型:圆柱形永磁体两侧并行排列螺旋线圈.分析了永磁铁尺寸对磁场涡流的影响以及电...     

吸水树脂吸液率测定方法分析及研究

本文综述了吸水树脂吸液率及其测定方法的现状 ,提出用 10 0目筛子过滤法作为测定吸液率的通用方法。并以合成的几个超强吸水树脂产品为例 ,测定出其吸纯水率与同类文献产品相比显著超过文献产品值。对吸液率测定中树脂浸泡用水量和泡时间的影响作了探索。     

Effect of plasticity on the residual stress measurement using the groove method

The mechanical methods based on milling rectilinear or annular grooves on a component's surface and measurement of relaxed strains are some of the most used semi-destructive methods for the determination of residual stresses. These are evaluated from the relaxed strains by means of equations based upon the linear elastic theory. In this paper the errors due to yielding localised at the bottom of the groove have been investigated. The analyses were carried out by means of the finite element technique varying the most important parameters involved. The experimental results show a good agreement with the numerical ones.     

添加致孔剂制备树脂基活性炭及电容性能研究

以碱性条件下合成的热固性酚醛树脂(PF)为原料,聚乙烯醇缩丁醛(PVB)和聚乙烯二醇(PEG)为致孔剂,采用聚合物共混炭化活化法制备双电层电容器用活性炭材料.通过热重(TG)分析探讨了PF,PF与PVB、PEG的共混物在炭化过程中的热解行为.考察了活化温度和活化时间对所得活性炭的收率、BET比表面积、孔径分布和比电容的影响,并进一步探讨了以这种活性炭材料作电极的双电层电容器的电容性能.结果表明,随着活化温度的升高,活化温度对活性炭收率的影响更为显著,所得活性炭的收率下降.聚合物PEG较PVB更适合作为成孔剂来控制活性炭的中孔孔径分布.酚醛树脂基活性炭电极比电容在850℃活化1 h为79.2F/g,而聚乙烯二醇/酚醛、聚乙烯醇缩丁醛/酚醛混合树脂基活性炭电极比电容则分别高达130.5和145.6F/g.     

An experimental method for measurement of strain distribution between wood the flour particles and polymer matrix on micro-mechanical level

Wood plastic composites (WPCs) are comprised of wood flour and thermoplastic polymer. The matrix is typically high-density polyethylene, poly (vinyl chloride), or polypropylene. The effect of morphology and micromechanics of wood flour particles on the mechanical performance of the bulk composite is a relatively unexplored area. The knowledge about the in situ properties of wood particles and the interfacial properties between the wood particles and the polymer matrix in the bio-composites is very limited. The objective of this work is to characterize the full-field deformation and strain distribution in and around wood particles embedded in polymer matrix. The mechanical tests are performed in small-scale tensile loading stage on thin composite samples containing 1-3 wood particles orientated at various angles. The deformations and strains is measured using optical measurement system based on Digital Image Correlation (DIC) principle.