纳米粘土增强环氧树脂复合材料抗原子氧性能的研究（英文）

本文采用激光爆破法高能原于氧束源研究了纳米粘土增强坏氧树脂复合材料的抗原子氧性能.研究了四种样品:纯环氧树脂,纳米粘土含量为1 wt%,2 wt%和4 wt%的纳米粘土增强环氧树脂复合材料,结果表明腐蚀深度随着纳米粘土含量的增加而降低,当掺杂纳米粘土含量为4 wt%时,腐蚀深度为纯环氧树脂腐蚀深度的28%～37%;X射线光电子能谱(XPS)分析表明原子氧轰击后,材料表面C-C/C-H键比例减少,C-O键、酮类比例增加,表面氧化程度增加,掺杂纳米粘土的材料表面生成了新的碳酸盐,掺杂4 wt%纳米粘土的复合材料表面氧化程度增加最小;扫描电子显微镜(SEM)结果显示含有纳米粘土的复合材料表面被原子氧轰击后在纳米粘土团簇处形成了"块状"物质,掺杂4 wt%纳米粘土的复合材料,"块状"物质尺寸和分布密度最大;综合腐蚀深度,XPS,以及SEM结果表明,虽然所有表面都一定程度地被原子氧腐蚀和氧化,但掺杂纳米粘土的复合材料表面由于生成了"块状"物质,阻挡了原子氧进一步腐蚀其下的材料,提高了抗原子氧性能.     

纳米SiO_2/环氧树脂复合材料介电性与纳米粒子分散性关系

利用硅烷偶联剂改性纳米SiO_2,制得改性纳米SiO_2分散液和改性纳米SiO_2颗粒.分别利用"机械法"和"气泡法"制备纳米SiO_2含量为2 wt%,3 wt%,4 wt%,5 wt%和6 wt%的未改性纳米SiO_2复合环氧树脂和改性纳米SiO_2复合环氧树脂,测试了复合环氧树脂的击穿特性和耐电晕特性.测试结果表明,复合环氧树脂的击穿场强和耐电晕性随纳米SiO_2含量的增加而增加,击穿场强在5 wt%纳米SiO_2含量时达到最大值,"气泡法"制备的改性纳米SiO_2复合环氧树脂的击穿场强和耐电晕性优于所制备的其他复合环氧树脂.以5 wt%纳米SiO_2含量复合环氧树脂为例,通过森下氏分散指数(Morisita’s index)方法对复合环氧树脂中纳米SiO_2的分散性进行定量表征,得出"气泡法"制得的纳米SiO_2/环氧树脂复合材料的分散性优于"机械法"制备的复合材料.研究发现纳米SiO_2在环氧树脂基体中分散性越好,复合材料的击穿特性和耐电晕性越好.     

细菌纤维素模板法制备p-Co_3O_4/n-ZnO复合材料及气敏特性研究（英文）

本文利用细菌纤维素为模板制备了p型Co_3O_4修饰的n型ZnO纳米复合材料,通过XRD、SEM、HRTEM、EDS和XPS等手段对纳米复合材料的组成、形貌与元素分布进行了相应的表征.相对于纯ZnO来说,p-Co_3O_4/n-ZnO复合材料对有机挥发性气体响应的灵敏度有明显提升,例如复合材料对100 ppm丙酮的灵敏度为63.7(最佳温度为180℃),是纯ZnO(最佳温度为240℃,灵敏度为2.3)的26倍.从材料表面氧空位(缺陷控制)、Co_3O_4的催化活性以及p-n异质结三个方面解释了复合材料对VOCs的高响应特性.同时细菌纤维素可以作为模板设计功能化的异质结复合物用于VOCs的测试或者其他应用.     

显微红外光谱法研究聚丙烯纳米复合材料的光氧化降解

采用显微红外(AIM)光谱法,结合偏光显微镜(POM)和扫描电子显微镜(SEM),对聚丙烯/碳酸钙(PP/CaCO₃)和聚丙烯/二氧化硅(PP/SiO₂)纳米复合材料中光氧化降解沿深度的分布进行了研究。结果表明,无论是纯聚丙烯还是聚丙烯纳米复合材料,试样的光氧化降解都是氧扩散控制过程,由表面逐渐向内部发展。纳米碳酸钙和纳米二氧化硅的加入都显著地促进了PP基体的光氧化降解,二氧化硅的影响更为严重。纳米填料的含量越高,复合材料的氧化程度也越高,但氧化层的厚度却基本不变,都在200 μm左右,当样品表面严重老化至表面脱落后,氧化继续向内部进行。氧化层的厚度主要是由试样成型过程中形成的表面过渡区的厚度决定的。     

化整为零:聚合物/粘土纳米复合材料的微观结构和阻隔性能

在聚合物基体中掺入少量的层状硅酸盐所制备的聚合物／粘土纳米复合材料，其阻隔性能明显地优于纯聚合物及其传统的复合材料。实验及分析结果表明，聚合物／粘土纳米复合材料的微观结构和阻隔性能主要受控于粘土剥离后的径厚比．一简单的重整化群模型被用来评估粘土几何因素（诸如径厚比、取向、剥离程度等）对聚合物／粘土纳米复合材料阻隔性能的影响，所得到的逾渗阈值及最佳粘土含量与实验结果吻合。     

空间材料抗原子氧有机涂层防护作用的光谱分析

用Fourier变换红外光谱(FTIR)、光电子能谱(XPS)和扫描电镜(SEM)对在模拟原子氧(AO)环境中,空间材料及在其表面涂覆的有机防护涂层的表面所发生的侵蚀与防护作用进行了研究。结果表明：采用环氧树脂、聚胺脂、醇酸树脂作为防护涂层,经AO辐照后,它们的表面形貌均发生了较大变化,腐蚀严重;而用有机硅涂层的表面形貌变化却甚小,具有较明显的防护效果。光谱分析表明,这种防护作用缘于有机硅涂层表面经AO辐照后生成了致密的氧化硅膜层,对抑制AO的进一步侵蚀起到了抑制作用。     

聚酰亚胺/钽铌酸钾纳米颗粒复合材料结构与机械性能分子动力学模拟

利用多尺度建模方法构建了聚酰亚胺/钽铌酸钾纳米颗粒复合物模型, 通过分子动力学模拟研究了不同尺寸钽铌酸钾纳米颗粒(5.5, 8.0, 9.4, 10.5, 11.5 Å)对复合材料的结构、弹性模量和相互作用能的影响规律, 并通过计算纳米颗粒表面原子键能和单位表面积原子数目探究了复合物机械性能提高的内部机理. 聚酰亚胺和聚酰亚胺/钽铌酸钾复合材料的杨氏模量分别为2.91和3.17 GPa, 泊松比分别为0.37和0.35, 钽铌酸钾纳米颗粒的引入可以显著改善聚酰亚胺的机械性能. 纳米颗粒表面原子的键能为8.62-54.37 kJ·mol^-1, 表明颗粒与基体主要通过范德华力作用结合且有氢键存在. 计算结果表明, 相同掺杂比例下, 纳米颗粒尺寸越小, 纳米颗粒表面原子数目越大, 颗粒与基体作用更强, 杨氏模量的提高幅度越大, 尺寸效应越显著. 因此, 掺杂小尺寸纳米颗粒是提高聚酰亚胺机械性能的有效途径.     

Ag NPS/g-C3N4纳米复合材料制备及其SERS纳米传感器

通过化学氧化块状石墨型氮化碳(g-C3N4),获得在水中分散性好的片状g-C3N4.XRD,FTIR和XPS表明,所得片状g-C3N4含有氧官能团.这不仅可以作为锚定点负载纳米银粒子(Ag NPs),而且可以获得Ag NPs均匀分散的Ag NPS/g-C3N4纳米复合物.制备的复合材料中银纳米颗粒的重量百分比也会随着硝酸银与片状g-C3N4的质量变化而发生变化.基于g-C3N4对Co2+的明显的拉曼强度响应,Ag NPS/g-C3N4纳米复合物作为表面增强拉曼散射(SERS)传感器检测Co2+.通过拉曼强度的对照,发现随着Co2+浓度的增加,拉曼信号增加;而含有73％银纳米颗粒的Ag NPS/g-C3N4纳米复合物有高的灵敏性,检测极限浓度达到10-9 mol·L-1;复合材料同时显示出高的选择性,对其他如Cd2+,Cu2+和Zn2+的金属离子没有明显的拉曼增强信号.分析了复合材料对Co2+的增强机制.由于Co2+与g-C3N4中的=N-/-NH-基团的耦合,引发复合材料中Ag NPs聚集,从而产生局部电磁场,进而产生表面增强效应.可以预知,Ag NPS/g-C3N4纳米复合物将作为一种用于制造SERS传感器的新的理想材料.     

细菌纤维素模板法制备p-Co3O4/n-ZnO复合材料及气敏特性研究

本文利用细菌纤维素为模板制备了p型Co₃O₄修饰的n型ZnO纳米复合材料，通过XRD、SEM、HRTEM、EDS和XPS等手段对纳米复合材料的组成、形貌与元素分布进行了相应的表征. 相对于纯ZnO来说，p-Co₃O₄/n-ZnO复合材料对有机挥发性气体响应的灵敏度有明显提升，例如复合材料对100 ppm丙酮的灵敏度为63.7(最佳温度为180 °C)，是纯ZnO(最佳温度为240 °C，灵敏度为2.3)的26倍. 从材料表面氧空位(缺陷控制)、Co₃O₄的催化活性以及p-n异质结三个方面解释了复合材料对VOCs的高响应特性. 同时细菌纤维素可以作为模板设计功能化的异质结复合物用于VOCs的测试或者其他应用.     

铁氮共掺杂纳米TiO_2复合膜的制备、光谱分析及光催化活性研究

用溶胶-凝胶法制备铁、氮共掺杂纳米TiO2凝胶,浸渍-提拉法将其镀膜于载玻片表面,经干燥、煅烧,制得Fe-TiO2-xNr复合膜;用XRD,SEM,XPS及UV-Vis对镀膜样品进行了表征.XRD分析表明,Fe-TiO2-xNr膜为锐钛矿结构,少数氮原子替代了TiO2晶格中的氧;SEM照片说明,构成膜的粒子分散均匀,形貌一致,粒径约19 nm:UV-Vis漫反射光谱显示,Fe3+掺杂可使复合膜对可见光的响应红移至740nm处;XPS图谱证明,铁、氮的掺入降低了Ti(2p3/2)电子结合能,从而拓宽了TiO2在可见光区的吸收范围.以光催化降解苏丹红I为模型反应,比较了不同掺杂样品的光催化活性,结果表明,当掺杂的Fe3+相对于Ti4-1的原子比达到0.4%时,复合膜表现出最佳催化性能,4 h后对苏丹红I的降解率达到97%.方法制备的氮和适量铁共掺杂Fe-TiO2-xNr复合膜能协同提高TiO2对可见光的响应能力及光催化活性,在污水处理领域具有潜在的应用价值.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.