Crystallization induced enhancement on electrical conductivity and strength of highly conductive PP composites

A highly conductive and reinforced polypropylene/nickel coated glass fiber (PP/NCGF) composite is fabricated via a simple and efficient strategy. Nucleating agent induced crystallization leads to the sharp volume excluded effect and drives NCGFs into the amorphous region of PP matrix, thus the formation of conductive network connected by NCGFs is promoted remarkably. The incorporation of nucleating agent dibenzylidene sorbitol (DBS) improves the strength of composites simultaneously due to the enhanced crystallinity and the reinforced interfacial interaction. Accordingly, the percolation threshold of PP/NCGF composites is decreased to 0.35 vol% (Ni content) by loading DBS, and the conductivity increases by four order of magnitude around the percolation threshold which exceeds 70 S/m with the Ni content of only 0.47 vol%. The tensile strength of PP/NCGF composites is increased by about 30–40 % in all range of NCGF content. This exciting result provides a strategy to prepare high-performance conductive composites by crystallization-induced enhancement.

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Graphical abstract Nucleating agent induced crystallization leads to the sharp volume excluded effect and drives Ni coated glass fibers into the amorphous region of PP matrix, thus the formation of conductive network is promoted remarkably. The incorporation of nucleating agent improves the strength of composites simultaneously due to the enhanced crystallinity and the reinforced interfacial interaction.

     

3D网状结构TiBw/Ti60复合材料高温力学性能

利用反应热压技术制备了3D网状结构Ti Bw/Ti60复合材料,对复合材料在600~750℃范围内的高温力学性能进行了测试。结果表明,与Ti60合金相比,3D网状结构Ti Bw的原位形成显著提高了复合材料高温强度。在600、650、700和750℃,5.1%(体积分数)Ti Bw/Ti60复合材料的抗拉强度相比Ti60合金分别提高了42.5%、39.9%、35%和13.2%,而延伸率在各温度下均低于基体合金。网状结构复合材料断裂时形成的主裂纹沿网状界面处扩展,且断裂机制随实验温度增加而改变。     

浅谈引气剂在混凝土中的应用

阐述了引气剂在混凝土中的作用机理以及影响混凝土含气量的因素，介绍了引气剂对新拌混凝土性能和硬化混凝土的耐久性、抗压强度、抗弯拉强度等性能的影响。     

Structure and properties of films fabricated from chitin solution by coagulating with heating

In the present work, chitin films were fabricated from chitin solution dissolved in 8 wt % NaOH/4 wt % urea aqueous systems at low temperature by coagulating with heating without using any coagulant. The formation of the chitin films was confirmed to be an entirely physical process, namely chitin inclusion complex associated with NaOH, urea and water in the solvent was broken by heating, leading to the aggregation of the chitin chains through the hydrogen bonding. A schematic model was proposed to describe the regeneration mechanism of the chitin, indicating the physical crosslinking and entanglement of the chitin chains to form the films. Glycerol was used as plasticizer, and with an increase of the glycerol content, the elongation at break (?_b) of chitin films increased rapidly from 7.8 to 83.1%, whereas the tensile strength (σ_b) decreased from 89.3 to 51.7 MPa. This work provided a “green” pathway for the researches and developments of chitin materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39538.     

High performance films of cellulose butyral derivative having a necklace-like annular structure in the side chains

We fabricated high performance films using cellulose butyral (CB) synthesized from native cellulose. Two-step reactions were adopted to produce the derivative CB, including etherification of cellulose with glycidol in NaOH/urea aqueous solution to yield O-(2,3-dihydroxypropyl) cellulose (DHPC), and butyralization of DHPC. Both DHPC and CB products were easily processed into a thin film by hot-press molding. The butyral modifier significantly improved the tenacity of highly ductile DHPC, by virtue of the possible chain-entangling action of the ring structures in the stretching process. Thereby the film toughness was markedly enhanced. The CB films exhibited excellent optical transparency and a good adhesive property to glass plates. Thus the films may be comparable to commercial poly(vinyl butyral) (PVB) films in optical and mechanical performances and therefore possess a potential applicability as interlayer for laminated glasses.     

延迟焦化装置辐射炉进料增加轻蜡油的技术改造分析

在对中石油西北某厂延迟焦化装置进行的扩能改造中,采用了辐射炉增加轻蜡油的工艺技术。改造结果说明,利用轻蜡油循环,改变辐射进料循环比,增产汽柴油收率并降低能耗,经济效益显著。     

柳钢中板轧机工作辊的选择和使用

本文对比分析了轧辊的类型、硬度及技术经济指标,确定了工作轧辊的选择依据,并对生产中出现的实际问题提出了相应的措施。     

CS-444碳硫分析仪数据传输装置

通过对CS-444碳硫分析仪数据自动传输功能软硬件的研究,开发了一种数据自动传输装置,实现了分析数据的远程传输.     

考虑上部荷载影响区的筏板抗浮锚杆布置方法研究

由于地下水浮力及上部荷载对地下结构筏板的作用方式不同,将抗浮锚杆满堂均布于底板的方式会使各锚杆受力不均匀,本文以单建式筏板基础的二层地下结构为模拟研究对象,利用有限元法建立数值计算分析模型,对底板厚度、柱轴力、地下水头等因素影响板底土反力进行计算,由此分析了柱下板底的上部荷载影响区的主要特征;在柱跨板块下采取满堂均布、...     

基于EEMD-KNN的机车牵引座状态识别方法

机车牵引座的安全可靠性对机车运行的安全性起到重要作用,因此对机车牵引座状态识别研究具有重要的经济价值和社会意义。为了开展牵引座的正常、小裂纹、大裂纹等3种状态识别研究,搭建机车牵引座的模拟实验台,用加速度传感器采集不同状态的振动信号,对原始数据进行时域特征提取,并进行集合经验模态分解(EEMD)提取时频域特征,采用K邻近算法(KNN)进行牵引座状态识别。实验结果表明：基于EEMD-KNN模式识别方法能对机车牵引座状态进行有效识别,识别率达到83.3%;而且添加时域特征之后的识别率更高一些,识别率达到90.5%。