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91.
以己内酰胺(CL)和十二内酰胺(LL)为单体,采用阴离子开环共聚制备尼龙6/12(PA6/12)共聚物,主要研究了LL添加量对共聚物热性能、结晶性能、力学性能和断面形貌的影响。研究结果表明,LL的添加量由0%增加到30%时,PA6/12共聚物熔融温度从218.0℃降低到182.6℃,结晶温度由168.9℃降至117.8℃,晶型结构未发生明显变化,但其结晶度由22.88%降低至13.58%,拉伸性能和弯曲性能都有一定程度降低,断裂伸长率由60%增大到325%,并在共聚物拉伸断面观察到大量直径为100nm、长度为1μm左右的纳米纤维状物质。 相似文献
92.
采用自孕育法制备新型的ZA92镁合金,研究了冷却槽对组织的细化作用,并对其机理进行了分析。结果表明:合金熔体内部的形核与冷却槽的激冷作用、熔体的流动速度及剪切力的大小有关,合适的冷却槽角度有利于晶粒的游离和增殖。熔体在流经冷却槽的过程中,其组织变化趋势为:粗大枝晶→细小枝晶→等轴晶→蔷薇状晶和近球状晶。冷却槽角度较大或较小均不利于组织的细化,当冷却槽角度在30~45°之间时,坯料组织的晶粒分布比较集中且细小,其平均晶粒尺寸在47.5~51.4μm之间。 相似文献
93.
94.
Crystallization‐Induced Emission Enhancement of a Deep‐Blue Luminescence Material with Tunable Mechano‐ and Thermochromism 下载免费PDF全文
Zhen Wu Shenzhong Mo Lina Tan Bing Fang Zhiqiang Su Yantu Zhang Meizhen Yin 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(40)
Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli‐responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine‐based spacer. This amide‐rich molecule offers many possibilities for forming intra‐ and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as‐prepared two‐component cocrystalline material displays an exceptive deep‐blue emission, which is extremely rare among naphthalimide‐based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual “turn off” thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid‐state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system. 相似文献
95.
The Influence of Carbon Nitride Nanosheets Doping on the Crystalline Formation of MIL‐88B(Fe) and the Photocatalytic Activities 下载免费PDF全文
Zhen‐Dong Lei Yuan‐Cheng Xue Wen‐Qian Chen Lin Li Wen‐Hui Qiu Yong Zhang Liang Tang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(35)
In this research, bulk graphitic carbon nitride (g‐C3N4) is exfoliated and transferred to the carbon nitride nanosheets (CNNSs), which are then coupled with MIL‐88B(Fe) to form the hybrid. From the results of the powder X‐ray diffraction, scanning electronic microscopy and thermogravimetric analysis, it is found that the doping of CNNSs on the surface of MIL‐88(Fe) could maintain the basic structure of MIL‐88B(Fe), and the smaller dimension of CNNSs might influence the crystallization process of metal‐organic frameworks (MOFs) compared to bulk g‐C3N4. Besides, the effects of the CNNSs incorporation on photocatalysis are also investigated. Through the photoluminescence spectra, electrochemical measurements, and photocatalytic experiments, the hybrid containing 6% CNNSs is certified to possess the highest catalytic activity to degrade methylene blue and reduce Cr(VI) under visible light. The improvement of the photocatalytic performance can be attributed to the matched energy level which favors the formation of the heterojunctions. Besides, it promotes the charge migration such that the contact between MOFs and CNNSs is more intimate, which can be inferred from the electronic microscopy images. Finally, a possible photocatalytic mechanism is put forward by the relative calculation and the employment of the scavengers to trap the active species. 相似文献
96.
A Two‐Stage Annealing Strategy for Crystallization Control of CH3NH3PbI3 Films toward Highly Reproducible Perovskite Solar Cells 下载免费PDF全文
Jing Zhang Wensheng Liang Wei Yu Shuwen Yu Yiliang Wu Xin Guo Shengzhong Liu Can Li 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(26)
The solvent‐engineering method is widely used to fabricate top‐performing perovskite solar cells, which, however, usually exhibit inferior reproducibility. Herein, a two‐stage annealing (TSA) strategy is demonstrated for processing of perovskite films, namely, annealing the intermediate phase at 60 °C for the first stage then at 100 °C for the second stage. Compared to conventional direct annealing temperature (DHA) at 100 °C, using this strategy, MAPbI3 films become more controllable, leading to superior film uniformity and device reproducibility with the champion device efficiency reaching 19.8%. More specifically, the coefficient of variation of efficiency for 49 cells is reduced to 5.9%, compared to 9.8% for that using DHA. The TSA process is carefully studied using Fourier transform infrared spectroscopy, X‐ray diffraction, and UV–vis absorption spectroscopy. It is found that in comparison with DHA the formation of hydrogen bonding and crystallization of perovskite are much slower and can be better controlled when using TSA. The improvements in film uniformity and device reproducibility are attributed to: 1) controllable MAPbI3 crystal growth stemming from the progressive formation of hydrogen bonding between methylammonium and halide; 2) suppression of intermediate phase film dewetting, which is believed to be due to its decreased mobility at the initial low‐temperature annealing stage. 相似文献
97.
以20CrMnTi钢为例,建立了连续冷却渗碳模型;对变温渗碳质量进行了分析计算;对渗碳后的组织情况进行预测,从而对变温渗碳的可行性进行了理论论证. 相似文献
98.
针对煮糖过程蔗糖结晶图像的特点,采用颜色空间转换的方法,将图像从RGB颜色空间转换到HSI颜色空间,利用HSI颜色空间各分量相对独立性以及结晶颗粒和糖浆溶液的色调差异通过改进的大津法对H分量进行阈值分割,再通过数学形态学,中值滤波,孔洞填充,去除噪声颗粒,去除图像边界的非完整颗粒等方法进行后续处理,最终将结晶颗粒从复杂的图像信息中分割出来。实验证明该方法分割效果好,切实可行。 相似文献
99.
100.