Preparation of proanthocyanidin–chitosan complex and its antioxidant and antibacterial properties

Chitosan (CS) is a natural polysaccharide with beneficial effects on human health. To further strengthen its biological properties, a CS-based complex was prepared by combining it with proanthocyanidin (PA) and named it as PA–CS in this study. The successful preparation of PA–CS was confirmed by Fourier transform infrared spectroscopy. The size of PA–CS particles was distributed between 10 and 100 µm with a mean value of 30.6 µm and low pH and high salt concentration could increase their swelling ratio. The loading capacity of PA in PA–CS particles was 82.2?±?1.7 mg/g, and an increased release of PA from the complex occurred at low pH and high salt concentration. After combination, PA–CS complex exhibited better antioxidant activity than CS, which is a result of the synergistic effects of PA and CS. The reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of PA–CS complex are mainly attributed to PA, whereas the superoxide radical scavenging activity of PA–CS complex largely depends on CS. Moreover, PA–CS complex showed similar diameters of inhibitory zone and identical minimal inhibitory concentrations compared with CS, suggesting that the antibacterial potential of PA–CS complex is similar to that of CS. In addition, after 20 days storage, PA–CS complex did not exhibit significant changes in DPPH radical scavenging activity and antibacterial activity, indicating the good stability of this complex.     

纳米NiO掺杂Carbores'P对Al2O3-C耐火材料力学性能的影响

为提高低碳铝碳耐火材料的力学性能,以≤1 mm的棕刚玉、Si粉和Carbores’P为原料,外加纳米NiO为催化剂,制备Al2O3-C基质试样,利用XRD、SEM、激光拉曼光谱研究纳米NiO对Carbores’P炭化产物的影响。以棕刚玉(粒度为5~3、3-1、≤1 mm)、电熔白刚玉粉、Si粉、鳞片石墨、Carbores’P、纳米NiO为原料制备低碳Al2O3-C试样,研究纳米NiO掺杂Carbore’P对试样力学性能的影响。结果表明:1400℃埋碳热处理后,添加纳米NiO能提高基质的石墨化度,促进碳纳米管和SiC晶须的生成;正是由于它们的生成,提高了Al2O3-C试样的致密度、常温强度和断裂前的位移量,使试样韧性增强。     

Excellent Mechanical and Transparency Properties of Cationic Waterborne Polyurethane Films Modified by Boehmite Sol

The strategies for nanosol from metal alkoxide have enabled production of ultratransparent and mechanically robust polymer nanocomposites at extremely high loading. Herein, a simple approach to fabricate high‐performance polyurethane‐based nanocomposites via unmodified boehmite nanoparticles is reported. Evaluating their physical properties, the uniform dispersion of boehmite in the matrix caused nanocomposites retains ultrahigh transparency. Hydrogen bonding and intermolecular entanglement between boehmite and polyurethane brings about the mechanical properties of the nanocomposites material enhanced, i.e., strength, stiffness, and toughness. Optimized strength, stiffness, and toughness of Boehmite/Cationic waterborne polyurethane at 40 wt% (BNC40) are up to 58.1 MPa, 1096.7 MPa, 249.5 MJ m^?3, respectively. Furthermore, the feasibility and mechanism of polymer strengthening and toughening by inorganic rigid nanoparticles is explored from the aspects of crystallinity and micromorphology.     

太赫兹波计算鬼成像:原理和展望

本文立足于太赫兹波成像领域近年来备受关注的研究热点—太赫兹波计算鬼成像,首先回顾了鬼成像从量子到经典再到计算的历史过程,然后阐述了计算鬼成像的数学原理,随后综述了计算鬼成像在太赫兹波段的发展历程,及其在超衍射分辨成像、石墨烯光电导成像、太赫兹光谱成像等方面的应用,并在最后展望了太赫兹波计算鬼成像的发展前景:计算鬼成像作为一种成像手段,可以绕开在太赫兹频段缺乏经济高效的焦面阵列式探测器的难题,但目前的成像帧率还难以满足快速成像的应用需求,相信在未来随着器件性能的提升和成像算法的优化,其成像帧率可以得到大幅提升。     

Halogenation effect promoted low bandgap polymers based on asymmetric isoindigo unit with low energy loss

To optimize the energy levels of the structural framework of isoindigo polymers, a series of asymmetric isoindigo based low bandgap polymers with chlorine, fluorine and thiazole substituents was constructed and their optical, electrochemical and photovoltaic properties were comparatively evaluated for the impact of different substitutions. In comparison with the polymer based on 2,2'‐bithiophene and isoindigo unit (PTi) with non‐substituted bithiophene as the donor moiety, the highest occupied molecular orbital energy level for the newly synthesized polymers is significantly decreased, and in turn an improvement of the open‐circuit voltage (V_OC) is noted in the corresponding photovoltaic devices. More importantly, combined with a low bandgap of 1.32 eV, the energy losses (E_loss) could be reduced to 0.61 eV for polymer based on chlorinated 2,2'‐bithiophene and isoindigo unit (PCl). In addition, the halogen moieties are observed to be superior in device fabrication and give better values than the thiazole substituent. Both fluorinated and chlorinated polymer donors exhibited improved performance compared with the original polymer PTi. Consequently, this work not only presents the influence of different electron withdrawing substituents on the physicochemical and photovoltaic performance, but also backs the concept of how to reduce the energy loss via the heteroatom effect. © 2020 Society of Chemical Industry     

锂电池回收再生石墨增强水泥性能研究

废弃锂离子电池的负极活性材料主要为石墨,现阶段对于废弃锂离子电池中的石墨主要采用填埋等方法进行处理,造成了资源的浪费和环境的污染。现有的研究表明,废弃锂离子电池中的石墨经高温热解及酸浸处理后可以得到纯净的再生石墨,采用再生石墨增强水泥基复合材料的力学性能和电学性能。结果表明：再生石墨的引入可以增强材料的抗压性能和抗折性能,最大增幅分别达到了57.3%和84.4%。此外,再生石墨的加入有效降低了材料的电阻率,减少了极化时间,当再生石墨的掺加量为3%时,养护28 d后材料的电阻率仅为249 Ω·cm。该复合材料还具有典型的压敏特性。所制备的复合材料有望用于混凝土材料结构的实时动态监测。此外,对于废弃锂离子电池的全组分回收利用及功能水泥材料的研发具有重要意义。     

开关磁阻直线电机的设计及其推力优化

设计了一种开关磁阻直线电机,使用JMAG软件对其进行了仿真和优化。进行了推力公式的推导,研究了导通顺序和初始位置对电机推力的影响,并分析了三种典型情况的磁力线分布。对电机的定子和动子的齿部和轭部高度、宽度及铁耗进行仿真优化,得出了最优参数。将有取向硅钢应用于该电机,研究了推力与轧制角的关系,并与使用普通硅钢的开关磁阻直线电机进行了对比,推力有一定提升。提出在动子齿部开切向槽的方案,结果表明,开切向槽对推力的影响较小,并能显著减小推力波动。     

掺杂EBS润滑剂的粉末冶金铝合金脱脂工艺研究

文章通过冷压-烧结制备了掺杂EBS润滑剂的粉末冶金铝合金,比较了单/多温段脱脂工艺优劣,发现多温段脱脂优于单温段脱脂,脱脂更彻底,但由于气体流量不能无限大,导致气氛脱脂得到的样品碳含量无法达到碳剩余理论值0.02%。研究了真空脱脂和空气负压脱脂机制,真空脱脂可使得EBS热分解的气态有机物和灰分从压坯表面逸出,并被及时带出炉外,最终合金碳含量接近碳剩余理论值0.02%；空气负压脱脂可使得残余碳被氧化逸出,脱碳更彻底,使样品碳含量低于碳剩余理论值。研究了脱脂工艺对合金力学性能的影响,真空脱脂合金力学性能优于气氛脱脂,相对密度最大为97.86%,拉伸强度最大为218.06MPa,接近未添加润滑剂合金的力学性能；空气负压脱脂虽然可使碳含量更低,但因脱脂过程中样品暴露在空气中,使得原料粉末也被氧化,导致最终的合金力学性能严重下降。