A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched ...A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.展开更多
基于breakup和collision液滴破碎模型采用Fluent和Gambit软件对平口喷嘴的真空射流雾化进行了模拟,研究了环境压力、喷射压力和喷嘴直径等参数对射流雾化结构和液滴索特平均直径(Sauter mean diameter,SMD)的影响。结果表明:①随着环境...基于breakup和collision液滴破碎模型采用Fluent和Gambit软件对平口喷嘴的真空射流雾化进行了模拟,研究了环境压力、喷射压力和喷嘴直径等参数对射流雾化结构和液滴索特平均直径(Sauter mean diameter,SMD)的影响。结果表明:①随着环境压力的降低,喷射束宽度减小,射流贯穿距离和SMD增加。当环境压力小于0.01 MPa时,各雾化性能参数的变化幅度减小;②环境压力和喷嘴直径一定,随着喷射压力的增加,喷射束宽度呈先快速后缓慢增加的趋势,而射流贯穿距离近似线性增加,SMD值变化不明显;③喷嘴直径越小,喷射束宽度和射流贯穿距离越大,SMD值越小,射流雾化效果越好,更易制备出光滑致密的聚合物薄膜。展开更多
为了对真空射流流场进行研究,应用Fluent软件并基于VOF（volume of fluid）方法、k-ε标准湍模型及PISO算法,对不同喷口直径及入射压力的直射式锥型流道喷嘴的射流流场速度和湍流运动分布进行了数值模拟分析.结果表明：1）入口压力相同...为了对真空射流流场进行研究,应用Fluent软件并基于VOF（volume of fluid）方法、k-ε标准湍模型及PISO算法,对不同喷口直径及入射压力的直射式锥型流道喷嘴的射流流场速度和湍流运动分布进行了数值模拟分析.结果表明：1）入口压力相同,喷嘴直径越大,射流与周围介质间的速度梯度越大,可促进射流的扩散和液滴破碎后的尺寸均匀分布;2）喷嘴直径一定,入口压力在10~15 MPa内,射流湍流强度分布达到最佳状态,射流流场较好;3）如果不考虑材料的溶解性,相对于三氯甲烷和四氯化碳,丙酮作为溶剂时的液体喷射雾化效果较好,适于制备质量较好的高分子薄膜.展开更多
为代替纤维素纸(C-P)基电解质膜用于铝空气电池,利用静电纺丝技术制备了聚吲哚/聚丙烯腈(PIN/PAN)聚合物基电解质膜。采用SEM和FTIR对PIN/PAN纤维表面形貌及化学组成进行了分析。通过电化学工作站和电池测试系统分析了PIN含量对PIN/PAN...为代替纤维素纸(C-P)基电解质膜用于铝空气电池,利用静电纺丝技术制备了聚吲哚/聚丙烯腈(PIN/PAN)聚合物基电解质膜。采用SEM和FTIR对PIN/PAN纤维表面形貌及化学组成进行了分析。通过电化学工作站和电池测试系统分析了PIN含量对PIN/PAN聚合物基电解质膜离子电导率、离子扩散系数及固态铝空气电池放电性能的影响。结果表明,PIN/PAN纤维的孔隙率、吸液率、断裂伸长率与加入的PIN含量有关,同时对碱性溶液具有良好的吸附能力及机械性能,其中,PIN含量(以PAN溶液的质量为基准,其中,溶剂为N,N-二甲基甲酰胺,下同)为4%的PIN/PAN纤维(记为4%PIN/PAN纤维)的吸液率达496%、孔隙率为87.1%、断裂伸长率为8.7%,分别是C-P的3.2、1.1、3.8倍。基于PIN/PAN纤维制备的PIN/PAN聚合物基电解质膜可有效提升固态铝空气电池性能。其中,4%PIN/PAN聚合物基电解质膜在3、5、7 m A/cm^(2)电流密度下,放电时长比C-P铝空气电池分别提升约18%、32%、38%,离子电导率为6.7×10^(–4)S/cm,离子扩散系数为2.69×10^(–8)cm^(2)/S。展开更多
In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also invest...In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and guest host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.展开更多
Stable thin films made from polyionic complex 2C12N+PVS- with incorporated Hb on PG electrodes were characterized by electrochemistry. The electron transfer between Hb and PG electrodes was greatly facilitated in micr...Stable thin films made from polyionic complex 2C12N+PVS- with incorporated Hb on PG electrodes were characterized by electrochemistry. The electron transfer between Hb and PG electrodes was greatly facilitated in microenvironment of 2C12N+PVS- films. The Hb-2C12N+PVS-films could be used to catalytically reduce trichloroacetic acid.展开更多
PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blend films were prepared by simple solution cast method using mixer of dimethyl sulphoxide (DMSO) and double distilled water (DDW) as a common solvent. Gamma ir...PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blend films were prepared by simple solution cast method using mixer of dimethyl sulphoxide (DMSO) and double distilled water (DDW) as a common solvent. Gamma irradiation studies have been carried out to investigate the potential for improvements in the electrical properties of pure and blend polymer film. The induced changes in the dielectric constant (εr), dielectric loss (tanδ) and AC conductivity (σac) properties for the unirradiated and irradiated films were studied, in the frequency range 50 Hz - 5 MHz at room temperature (27°C). Further, it was seen that the frequency dependent dielectric constant, dielectric loss and AC conductivity were found to increase with increasing γ irradiation dose for all the PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blends. The maximum σac at 1 kHz frequency was observed to be 2.4421 × 10-6 s/m (at room temperature) for PVA film irradiated at 1.5 kGy.展开更多
It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or hetero...It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q, independent of the density of rubbing-induced defects. Heterogeneous nucleation, on the otherhand, is identified for those with q increasing with increasing density of defects. Our result shows that PS films on oxidecoated silicon with thickness less than ≈ 13 nm are dominated by spinodal dewetting, but the thicker films are dominated bynucleation dewetting. We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in thedewetting film, contrary to the classic theory of Cahn.展开更多
文摘A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.
文摘基于breakup和collision液滴破碎模型采用Fluent和Gambit软件对平口喷嘴的真空射流雾化进行了模拟,研究了环境压力、喷射压力和喷嘴直径等参数对射流雾化结构和液滴索特平均直径(Sauter mean diameter,SMD)的影响。结果表明:①随着环境压力的降低,喷射束宽度减小,射流贯穿距离和SMD增加。当环境压力小于0.01 MPa时,各雾化性能参数的变化幅度减小;②环境压力和喷嘴直径一定,随着喷射压力的增加,喷射束宽度呈先快速后缓慢增加的趋势,而射流贯穿距离近似线性增加,SMD值变化不明显;③喷嘴直径越小,喷射束宽度和射流贯穿距离越大,SMD值越小,射流雾化效果越好,更易制备出光滑致密的聚合物薄膜。
文摘为了对真空射流流场进行研究,应用Fluent软件并基于VOF（volume of fluid）方法、k-ε标准湍模型及PISO算法,对不同喷口直径及入射压力的直射式锥型流道喷嘴的射流流场速度和湍流运动分布进行了数值模拟分析.结果表明：1）入口压力相同,喷嘴直径越大,射流与周围介质间的速度梯度越大,可促进射流的扩散和液滴破碎后的尺寸均匀分布;2）喷嘴直径一定,入口压力在10~15 MPa内,射流湍流强度分布达到最佳状态,射流流场较好;3）如果不考虑材料的溶解性,相对于三氯甲烷和四氯化碳,丙酮作为溶剂时的液体喷射雾化效果较好,适于制备质量较好的高分子薄膜.
文摘为代替纤维素纸(C-P)基电解质膜用于铝空气电池,利用静电纺丝技术制备了聚吲哚/聚丙烯腈(PIN/PAN)聚合物基电解质膜。采用SEM和FTIR对PIN/PAN纤维表面形貌及化学组成进行了分析。通过电化学工作站和电池测试系统分析了PIN含量对PIN/PAN聚合物基电解质膜离子电导率、离子扩散系数及固态铝空气电池放电性能的影响。结果表明,PIN/PAN纤维的孔隙率、吸液率、断裂伸长率与加入的PIN含量有关,同时对碱性溶液具有良好的吸附能力及机械性能,其中,PIN含量(以PAN溶液的质量为基准,其中,溶剂为N,N-二甲基甲酰胺,下同)为4%的PIN/PAN纤维(记为4%PIN/PAN纤维)的吸液率达496%、孔隙率为87.1%、断裂伸长率为8.7%,分别是C-P的3.2、1.1、3.8倍。基于PIN/PAN纤维制备的PIN/PAN聚合物基电解质膜可有效提升固态铝空气电池性能。其中,4%PIN/PAN聚合物基电解质膜在3、5、7 m A/cm^(2)电流密度下,放电时长比C-P铝空气电池分别提升约18%、32%、38%,离子电导率为6.7×10^(–4)S/cm,离子扩散系数为2.69×10^(–8)cm^(2)/S。
文摘In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and guest host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.
文摘Stable thin films made from polyionic complex 2C12N+PVS- with incorporated Hb on PG electrodes were characterized by electrochemistry. The electron transfer between Hb and PG electrodes was greatly facilitated in microenvironment of 2C12N+PVS- films. The Hb-2C12N+PVS-films could be used to catalytically reduce trichloroacetic acid.
文摘PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blend films were prepared by simple solution cast method using mixer of dimethyl sulphoxide (DMSO) and double distilled water (DDW) as a common solvent. Gamma irradiation studies have been carried out to investigate the potential for improvements in the electrical properties of pure and blend polymer film. The induced changes in the dielectric constant (εr), dielectric loss (tanδ) and AC conductivity (σac) properties for the unirradiated and irradiated films were studied, in the frequency range 50 Hz - 5 MHz at room temperature (27°C). Further, it was seen that the frequency dependent dielectric constant, dielectric loss and AC conductivity were found to increase with increasing γ irradiation dose for all the PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blends. The maximum σac at 1 kHz frequency was observed to be 2.4421 × 10-6 s/m (at room temperature) for PVA film irradiated at 1.5 kGy.
基金This work was supported by the Institute of Nano Science and Technology and the Hong Kong University of Science and Technology through the Postdoctoral Matching Fund.
文摘It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q, independent of the density of rubbing-induced defects. Heterogeneous nucleation, on the otherhand, is identified for those with q increasing with increasing density of defects. Our result shows that PS films on oxidecoated silicon with thickness less than ≈ 13 nm are dominated by spinodal dewetting, but the thicker films are dominated bynucleation dewetting. We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in thedewetting film, contrary to the classic theory of Cahn.
基金This work was supported by the Major State Basic Research Development Program(Grant No.G2000078102)the National Natural Science Foundation of China(Grant Nos.20204003.20334010.and 20473045)+1 种基金the Ministry of Education of China(Grant No.20020010006)863 High-Tec.Projeet(Grant No.2003AA302140).
