Structure of a poly(2,5‐benzimidazole)/phosphoric acid complex

As‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 2₁ chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004     

Colorimetric recognition of different enzymology-concerning transition metals based on a hybrid cluster complex.

A hybrid cluster complex, formed by chelating a chromogenic ligand to a [2Fe-2S] cluster, sensitively exhibited differential colorimetric responses towards Hg2+, Cd2+, Cr3+, Pb2, Sn2+, Cu2+, Zn2+, Fe3+ and Co2+ in water at physiological pH. Speciation of some of these metal elements, such as Cr(III) and Sn(IV), was also studied by UV/Vis absorption.     

Concentrations of hazardous heavy metals in environmental samples collected in Xiamen, China, as determined by vapor generation non-dispersive atomic fluorescence spectrometry.

Non-dispersive atomic fluorescence spectrometry (NDAFS) coupled with vapor generation (VG) sample introduction was applied to the determination of the concentrations of hazardous heavy metals, such as arsenic, cadmium, lead and mercury, in seawater, soils and total airborne particulate matter (PM) collected around the Xiamen area in China. Almost 100% sample introduction efficiency was achieved by using thiourea and ascorbic acid for the pre-reduction of As(V) to As(III), K3Fe(CN)6 and tartaric acid for pre-oxidation of Pb(II) to Pb(IV), and masking the interferences arising from the co-existing transition metals to As, Cd, Hg and Pb during their vapor generation process. Moreover, a novel sample pretreatment device was developed to avoid the loss of mercury, lead, cadmium and arsenic during sample pretreatment. With such methods, the detection limit (DL) of arsenic, cadmium, lead and mercury was down to 0.08, 0.03, 0.05, 0.01 ng mL(-1) (3sigma), respectively. The relative standard deviations (RSD, n = 11) for arsenic, cadmium, lead and mercury at 10 ng mL(-1) were 0.9%, 1.6%, 1.3% and 2.0%, respectively. The concentrations of hazardous heavy metals in the environmental samples collected in Xiamen, China are in the range from 0.02 +/- 0.001 ng mL(-1) in seawater to 15.3 +/- 0.2 microg g(-1) in soils. Besides flame/GF-AAS and ICP-AES/MS, VG-NDAFS should be another choice for the determination of hazardous heavy metals in environmental samples.     

利用声波控制超短脉冲的色散

 声光互作用器件声光可编程色散滤波器（AOPDF）是一种实时的色散补偿器件，它可用于飞秒啁啾脉冲放大系统。通过耦合模理论推导，得到了输出脉冲的群延迟与调制声波的频率、啁啾、带宽等参数的关系，并且对用2.5cm长的LiNbO₃作为声光晶体的AOPDF补偿飞秒光脉冲的色散进行了数值模拟，得到了对中心波长为800 mm的钛宝石飞秒激光色散补偿特性及所需声波的频率和啁啾参数。     

强流束晕-混沌的外部磁场开关控制

研究了强流离子束在周期聚焦磁场通道中束晕-混沌的外部磁场开关参数控制方法. 将该方法应用在多粒子模型中，实现了对5种不同初始分布质子束的束晕-混沌的有效控制，得到了消除束晕及其再生现象的理想结果.在强流加速器系统中，由于外部磁场是可测和可调 的物理量，因此该控制方法有利于实验研究，可为强流质子加速器中周期聚焦磁场的设计和实验提供参考. 关键词： 强流离子束 周期聚焦磁场通道 束晕_混沌 混沌控制 开 关控制     

超声速等离子体射流的数值模拟

基于可压缩的全Naiver-Stokes方程，利用PHOENICS程序对由会聚 辐射阳极形状等离子体炬产生的超声速等离子体射流进行了数值模拟.考虑了等离子体的黏性、可压缩性以及变物性对等离子体射流特性影响.研究了超声速等离子体射流的流场结构特性以及不同环境压力对等离子体射流产生激波结构的影响.结果表明，超声速等离子体射流在喷口附近形成的周期性激波结构是其和环境气体相互作用的结果. 关键词： 等离子体炬 超声速等离子体射流 PHOENICS     

离子束增强沉积VO2多晶薄膜的温度系数

用改进的离子束增强沉积方法和恰当的退火从V2O5粉末直接制备了VO2多晶薄膜.实验测试表明，薄膜的取向单一、相变特性显著、结构致密、界面结合牢固、工艺性能良好，薄膜的电阻温度系数（TCR）最高可达4.23%/K.从成膜机理出发，较详细地讨论了离子束增强沉积 VO2多晶薄膜的TCR高于VOx薄膜的TCR的原因.分析认为，单一取向的VO2结构使薄膜晶粒具有较高的电导激活能，致密的薄膜结构减少了氧空位和晶界宽度，使离子束增强沉积 VO2多晶薄膜结构比其他方法制备的VOx薄膜更接近于单晶VO2是其具有高TCR的原 关键词： VO2多晶薄膜 离子束增强沉积 热电阻温度系数     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法 ,在D形内包层掺Yb3 双包层光纤一端直接写制出Bragg光栅 ,用作双包层光纤激光器的输出腔镜 .试验得到了线宽为 0 196nm ,波长为 10 5 8 2nm ,最高输出功率为 5 70mW的稳定激光输出 ,解决了激光器中模式竞争造成的输出不稳定现象 .从速率方程出发 ,对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析 ,结果与实验符合很好     

Zn(BTZ)2白色有机电致发光材料的合成及其器件制备

以PCl₃为脱水剂,将邻氨基硫酚与水杨酸脱水环化合成出2-(2-羟基苯基)苯并噻唑,并进一步将所得产物与乙酸锌反应合成出2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ)₂)材料。以该配合物作为发光层制备出结构为ITO/PVK:TPD/Zn(BTZ)₂/Al近白色电致发光器件,其色坐标位于白场之内(x=0.242,y=0.359),在驱动电压为16V时,亮度达3200cdm²,对应的量子效率为0.32%。进一步在Zn(BTZ)₂中掺入橙红色染料Rubrene,制成ITO/PVK:TPD/Zn(BTZ)₂:Rubrene/Al结构器件,实现了纯白色发光(色坐标值:x=0.324,y=0.343),非常接近于白色等能点,且量子效率达0.47%。最后对上述器件的发光和电学性能进行了深入的研究和探讨。     

利用爆磁压缩发生器产生高功率脉冲高电压

 爆磁压缩发生器产生脉冲高电压技术可以用于产生高功率微波及强电磁脉冲的实验研究。给出了利用螺旋型爆磁压缩发生器（HEMG）驱动电爆炸丝功率调节系统产生高功率脉冲高电压的实验方法和主要的结果。在利用HEMG驱动电爆炸丝断路开关（EEOS）产生脉冲高电压实验中，获得了最高电压700~800kV,功率大于20GW的脉冲输出。