Microstructure and Thermal and Tensile Properties of Poly(vinyl alcohol) Nanocomposite Films Reinforced by Polyacrylamide Grafted Cellulose Nanocrystals

Abstract

Polyacrylamide grafted cellulose nanocrystals (CNC-g-PAM) were incorporated into poly(vinyl alcohol) (PVA) by a solution casting method to fabricate nanocomposite films with enhanced thermal and tensile properties. The microstructure and the thermal and tensile properties of the PVA/CNC-g-PAM nanocomposite films were investigated as a function of CNC-g-PAM content. Infrared spectroscopy corroborated the presence of hydrogen bonds between PVA and the PAM on the surface of the CNC. Polarized optical microscopy and scanning electron microscopy revealed good dispersion of the CNC-g-PAM in the PVA matrix and good interfacial compatibility. Accordingly, the initial degradation temperature of the nanocomposite films was elevated slightly compared to pristine PVA film. The glass transition temperature, melting temperature, and crystallinity of the PVA also varied slightly after the incorporation of the CNC-g-PAM. At both 0% and 50% RH, the nanocomposite films showed an obvious increase of elastic modulus, no apparent change of breaking strength and a drastic reduction of elongation at break with increasing CNC-g-PAM content.     

Highly efficient perovskite solar cells by tuning electronic structures of thienothiophene-based as hole transport materials

The atomic substitutions were used to study the hole transport materials (HTM) properties of six thiophenothiophene molecules (HTM1-HTM6) to reveal the relationship between their core structures and photoelectric properties. To better investigate the difference between experimentally original and designed molecules, we calculated the hole mobility and some parameters (such as energy levels, stability, and optical properties, etc). The results showed that the molecular orbital levels of the original and designed molecules have well matched with perovskite and Ag electrode to ensure hole transport and inhibit the electron reflux. Among the designed HTMs, HTM5 has the smallest energy gap that results in the red-shifted absorption spectra. Furthermore, there is an obviously increased charge transfer integral V due to the introduction of the Si atom, which greatly improved the hole mobility. Therefore, atom substitution by introducing Si atoms (HTM5) will improve the energy levels and charge transport ability, and molecular design by means of atom substitution can be a potential way to tunable HTM performance in solar cells.     

基于PdSe2/GaAs异质结的高灵敏近红外光伏型探测器的制备和图像传感的应用

本文制备了一种基于PdSe₂/GaAs异质结的高灵敏近红外光电探测器,该探测器是通过将多层PdSe₂薄膜转移到平面GaAs上制成的. 所制备的PdSe₂/GaAs异质结器件在808 nm光照下表现出明显的光伏特性,这表明近红外光电探测器可以用作自驱动器件. 进一步的器件分析表明,这种杂化异质结在零偏电压和808 nm光照下具有1.16×10⁵的高开关比. 光电探测器的响应度和比探测度分别约为171.34 mA/W和2.36×10¹¹ Jones. 而且,该器件显示出优异的稳定性和可靠的重复性. 在空气中2个月后,近红外光电探测器的光电特性几乎没有下降,这归因于PdSe₂的良好稳定性. 最后,基于PdSe₂/GaAs的异质结器件还可以用作近红外光传感器.     

Complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities

We theoretically study complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities. We investigate quantum dynamics of micro-micro and micro-macro entanglement in the micro-macro system. It is found that strong micro-macro entanglement between Rydberg impurities and the BEC can be generated by the use of initial micro-micro entanglement between two Rydberg impurities, which acts as the seed entanglement to create micro-macro entanglement. We demonstrate a curious complementarity relation between micro-micro and micro-macro entanglement, and find that the complementarity property can be sustained to some extent even though in the presence of the BEC decoherence.     

The existence and stability of bulk nanobubbles:a long-standing dispute on the experimentally observed mesoscopic inhomogeneities in aqueous solutions

In theory,nanobubbles can stably exist with a lifetime of microseconds at most,but numerous experimental observations demonstrate that nanobubbles in bulk solution can be stable from hours to weeks.Although various conjectures on the stability mechanism of bulk nanobubbles,such as the contaminant mechanism,skin mechanism,surface zeta potential mechanism,are proposed,there has not yet been a unified conclusion.Since bulk nanobubbles show great potential in a wide spectrum of applications and are relevant to a number of unsolved questions on cavitation and nucleation,the debate over their stability mechanisms has been active.In the past,extensive studies have been carried out to understand the mechanism of nanobubble stability,and important insights have already been provided.This paper will provide a brief overview of our current understanding of the unexpected stability of bulk nanobubbles.     

氮低温制冷循环系统在大科学装置中的应用与发展

大科学装置中低温设备的氮低温冷量需要日益快速增长,为减少能耗和保障装置的长期稳定运行,基于大科学装置氮低温系统运行需求,介绍了氮低温制冷循环系统在国内外大科学装置中的应用情况,总结了目前大科学装置中应用氮低温制冷循环系统的研究现状,并探讨以氮制冷机为核心的氮低温制冷循环系统在未来大科学装置中发展方向。     

电枢参数对电枢超导型高温超导电机性能的影响

高温超导材料存在背景磁场依赖性和各向异性的问题,针对超导感应电机采用双层绕组结构,提出了双重镜像法建立开口矩形槽内漏磁场垂直方向和水平方向的解析模型,利用该模型研究了超导线圈在传输不同电流情况下磁场分布规律,揭示了开口矩形槽电磁结构参数对槽内超导线圈所受表面磁场的影响规律。研究结果表明,适当增大槽宽尺寸可以有效降低超导线圈表面所受最大磁场,传输电流和线圈匝数均能够近乎线性增大超导线圈表面所受最大磁场。     

双子佯谬与星际航行

计算了在两个假想的星际航行方案中,与"双子佯谬"相关的时间差别.这种差别体现了惯性与非惯性参考系经历的时间有绝对差异,而不再是"相对"效应.     

不规则H形量子势垒增强AlGaN基深紫外发光二极管性能

针对AlGaN基多量子阱中有效的平衡载流子注入问题,研究了有源区势垒层中Al组分调制形成的非规则H形量子势垒对AlGaN基深紫外发光二极管(LED)器件性能的影响及载流子的输运行为。研究发现,与多量子阱中常用的单Al组分势垒相比,加入Al组分较高的双尖峰势垒可以有效地提高内量子效率和光输出功率。进一步研究表明,电子在有源区因凸起的尖峰势垒而得到了有效的阻挡,减少了电子的泄露,而空穴获得更多的动能从而穿过较高的势垒进入有源区。因此,采用非对称H形量子势垒的深紫外LED器件中载流子输运实现了较好的平衡,量子阱中的载流子复合速率远高于普通的深紫外发光二极管。     

一种限制周期气固两相流直接数值模拟中整体质量流率的新方法

全周期边界条件的气固两相流系统是研究气固相互作用的一个常用计算模型。为平衡周期气固系统在流向上的受力,常对系统施加平衡系统总重力的固定压力梯度,但由于数值误差的影响,这种固定压力梯度的方法会使得气固系统整体不断加速进而导致模拟失真。为了降低系统质心加速度的影响,本文先后采用了前人提出的固定整体质量流率方法和本文提出的压力梯度后验修正方法,并对两种方法的模拟结果进行了对比。