热氧老化对碳纤维织物增强聚合物基复合材料弯曲性能的影响

为了探索增强体结构对碳纤维增强聚合物基复合材料(CF-PMCs)热氧老化后弯曲性能的影响,对三维四向编织碳纤维/环氧复合材料(简称为三维编织复合材料)和层合平纹碳布/环氧复合材料(简称为层合复合材料)的热氧老化性能进行了研究。利用FTIR、老化失重、弯曲测试和SEM等手段分析了热氧老化前后的试样。结果表明:热氧老化导致基体树脂的氧化断链以及纤维/基体界面结合力的退化是两种复合材料弯曲强度和弯曲模量下降的原因,弯曲强度比弯曲模量更容易受热氧老化的影响。在相同的热氧老化条件下,层合复合材料的热氧老化失重大于三维编织复合材料的,而三维编织复合材料的弯曲强度和弯曲模量保留率均大于层合复合材料的。在140℃下老化1 200h后,层合复合材料的弯曲强度和弯曲模量保留率分别为74.7%和88.3%,而对应的三维编织复合材料的分别为79.4%和91.5%。因此,采用三维编织预制件作为CF-PMCs的增强体是一种有效的提高其热氧稳定性的方法。     

薄膜铝空气电池阴极复合催化剂性能研究

采用棒状alpha-MnO2作为阴极主催化剂,并掺杂La2O3和CeO2制成复合型催化剂,使用1 mm厚碱性凝胶聚合物电解质膜,组装成薄膜聚合物电解质铝空气电池。在0.5×10–3 A·cm–2电流密度下恒流放电考察不同阴极催化剂的性能,Mn-La和Mn-Ce型电化学性能均低于Mn-La-Ce型催化剂。随后的实验中,分别测试了薄膜铝空气电池在0.8×10–3和1.1×10–3 A·cm–2电流密度下的放电性能,并在1.1×10–3 A·cm–2电流密度下得到其容量密度为8.91×10–3 Ah·cm–2,能量密度为11.46×10–3 Wh·cm–2,以及功率密度为1.42×10–3 W·cm–2。     

纳米钛粉改性环氧底漆对GFEP飞机电磁屏蔽性能的影响

航空电子设备的发展和地面电磁波源的迅速增多对玻璃纤维增强环氧树脂(GFEP)机身结构飞机的运行安全构成了威胁,亟需提升此类机身结构的电磁屏蔽性能。介绍了电磁屏蔽效能的计算方法,提出了在GFEP飞机机身涂覆纳米钛粉改性环氧底漆的应对方案。制备了纳米钛粉质量分数为1.0%的改性环氧底漆,研究了改性底漆对GFEP飞机机身典型结构样品电磁屏蔽性能的影响。结果表明:在300 kHz~1.5 GHz的测试范围内,涂覆改性底漆的测试样品的电磁屏蔽效能良好,达到9.5~29.7 dB。     

空间光通信系统发射光束准直特性研究

提出一种前端直接耦合光纤平凸透镜的聚合物直光锥光准直系统.通过具体地对直光锥的端体结构参数进行优化设计以得到高耦合效率准直精度的直接耦合式聚合物直光准直系统.并利用光线传输理论和仿真实验,论证了直光锥的锥角和锥长准直效能的较大影响.结果表明,选择合适的锥角和锥长能达到十微弧度级准直精度,能较好地满足空间光通信系统远距离发射和接收对于光束质量的要求.此外,理论数值和仿真实验同样验证了该直接耦合式直光准直系统对于较大发散角的发散光束具有较好准直效果.     

Cohesively Enhanced Conductivity and Adhesion of Flexible Silver Nanowire Networks by Biocompatible Polymer Sol–Gel Transition

Silver nanowire (AgNW) networks are a promising candidate to replace indium tin oxide (ITO) as transparent conductors. In this paper, a novel transparent composite conductor composed of AgNW/biocompatible alginate gel on a flexible polyethylene terephthalate (PET) substrate, with synchronously enhanced adhesion and reduced resistivity, is prepared without high‐temperature annealing. The sheet resistance of the flexible AgNW/PET film reduces from 300 to 50.3 Ohm sq^?1 at transmittance of 94%. The optical and electrical performance is superior to that obtained from the flexible ITO film on PET. Meanwhile, the sheet resistance does not show great change after tape test, suggesting a good adhesion of AgNW to the polymer substrate. Moreover, the AgNW composite film shows a good stability to resist long‐term storage, solvent damage, and ultrasonication. Finally, polymer solar cells employing the composite AgNW film as the electrode are realized, displaying an efficiency of 2.44%.     

Highly Stretchable and Sensitive Strain Sensors Using Fragmentized Graphene Foam

Stretchable electronics have recently been extensively investigated for the development of highly advanced human‐interactive devices. Here, a highly stretchable and sensitive strain sensor is fabricated based on the composite of fragmentized graphene foam (FGF) and polydimethylsiloxane (PDMS). A graphene foam (GF) is disintegrated into 200–300 μm sized fragments while maintaining its 3D structure by using a vortex mixer, forming a percolation network of the FGFs. The strain sensor shows high sensitivity with a gauge factor of 15 to 29, which is much higher compared to the GF/PDMS strain sensor with a gauge factor of 2.2. It is attributed to the great change in the contact resistance between FGFs over the large contact area, when stretched. In addition to the high sensitivity, the FGF/PDMS strain sensor exhibits high stretchability over 70% and high durability over 10 000 stretching‐releasing cycles. When the sensor is attached to the human body, it functions as a health‐monitoring device by detecting various human motions such as the bending of elbows and fingers in addition to the pulse of radial artery. Finally, by using the FGF, PDMS, and μ‐LEDs, a stretchable touch sensor array is fabricated, thus demonstrating its potential application as an artificial skin.     

A Surface Tailoring Method of Ultrathin Polymer Gate Dielectrics for Organic Transistors: Improved Device Performance and the Thermal Stability Thereof

Tailoring the surface of the dielectric layer is of critical importance to form a good interface with the following channel layer for organic thin film transistors (OTFTs). Here, a simple surface treatment method is applied onto an ultrathin (<15 nm) organosilicon‐based dielectric layer via the initiated chemical vapor deposition (iCVD) to make it compatible with organic semiconductors without degrading its insulating property. A molecular‐thin oxide capping layer is formed on a 15 nm thick poly(1,3,5‐trimetyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) by a brief oxygen plasma treatment. The capping layer greatly enhances the thermal stability of the dielectrics, without degrading the original mechanical flexibility and insulating performance of the dielectrics. Moreover, the surface silanol functionalities formed by the plasma treatment can also be utilized for the surface modification with silane compounds. The surface‐modified dielectrics are applied to fabricate low‐voltage operating (<5 V) pentacene‐based OTFTs. The highest field‐effect mobility of the device with the surface‐treated 15 nm thick pV3D3 is 0.59 cm² V^?1 s^?1, which is improved up to two times compared to the TFT with the pristine pV3D3. It is believed that the simple surface treatment method can widely extend the applicability of the highly robust, ultrathin, and flexible pV3D3 gate dielectrics to design the surface of the dielectrics to match well various kinds of organic semiconductors.