烯烃聚合单活性中心非茂催化剂的最新研究进展

综述了近几年来烯烃聚合用单活性中心非茂催化剂的研究进展。简要介绍了 2 3种由前、后过渡金属组成的配位化合物催化剂的结构与性能     

Structure and properties of CE/CTBN/EP blends: II. Effect of EP on the mechanical properties and thermostability of the CE/CTBN system

Carboxyl‐terminated butadiene‐acrylonitrile rubber (CTBN) has often been used to improve the toughness of cyanate ester (CE) resin while sacrificing modulus and thermostability. In this paper, the addition of the appropriate amount of epoxy resin (EP) to the CE/CTBN system is shown to not only increase the modulus and thermostability of the blend, but also improve the toughness. The values of impact strength showed a maximum for the CE/CTBN/EP 100/5/5 blend. The temperature of 10 % weight loss (T₁₀) improves from 376 °C for CE/CTBN 100/5 to 407 °C for the CE/CTBN/EP 100/5/2.5 blend. It is proposed that addition of the appropriate amount of EP can decrease the mobility and increase the stability of CTBN via the reaction between the terminal carboxyl group of CTBN and the hydroxyl group of EP. But a very high EP concentration will decrease the crosslinking density of CE, consequently reducing the mechanical properties and thermostability of the blends. Copyright © 2004 Society of Chemical Industry     

Application of a multi-channel system for continuous monitoring and an early warning system.

A multi-channel continuous toxicity monitoring system developed in our laboratory, based on two-stage mini-bioreactors, was successfully implemented in the form of computer-based data acquisition. The multi-channel system consists of a series of a two-stage minibioreactor systems connected by a fiber optic probe to a luminometer, and uses genetically engineered bioluminescent bacteria for the detection of the potential toxicity from the soluble chemicals. This system can be stably and continuously operated due to the separation of the culture reactor from the test reactor and accomplish easy and long-term monitoring without system shut down by abrupt inflows of severe polluting chemicals. Four different recombinant bioluminescent bacteria were used in different channels so that the modes of the samples toxicities can be reasonably identified and evaluated based upon the response signature of each channel. The bioluminescent signatures were delivered from four channels by switching one at once, while the data is automatically logged to an IBM compatible computer. We also achieved the enhancement of the system through the manipulation of the dilution rate and the use of thermo-lux fusion strains. Finally, this system is now being implemented to a drinking water reservoir and river for remote sensing as an early warning system.     

A study on charge reduction in HfO/sub 2/ gate stacks

Charge in metal-organic chemical vapor deposition-grown HfO/sub 2/ gate stacks has been systematically studied using nMOS capacitors. It is found that, for these films, the charge in the stack is mainly concentrated at the interfaces between the layers and is negative at the HfO/sub 2//interfacial layer (IL) interface and positive at the Si/IL interface. In general, the calculated charge densities at both interfaces are of order 10/sup 12/ cm/sup -2/. A forming gas anneal (FGA) reduces both interface charge greatly. The FGA can also significantly reduce the hysteresis and interface state density. The effects of post deposition anneal at various temperatures and under various ambients have also been studied. It is found that a high-temperature dilute oxidizing ambient anneal followed by an FGA reduces the charge at both interfaces.     

Fabrication of multi-walled carbon nanotube reinforced polyelectrolyte hollow nanofibers by electrospinning

Hybrid hollow multi-walled carbon nanotubes (MWCNTs)/polyelectrolytes (PE) nanofibers were prepared by a combination of the electrospinning method and layer-by-layer (LbL) technique. The mixed polystyrene (PS)/MWCNTs nanofibers were obtained by electrospinning method, which were employed as templates to self-assembly multilayered polyelectrolytes by LbL technique. Hollow MWCNTs/PE nanofibers were obtained by selectively removed part of the template: PS, which is confirmed by Raman spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM).     

蓝湿皮酶软化的特性研究

以自行研制的一种复合酶为软化剂 ,研究了 p H值、反应温度、反应时间、酶用量以及铬含量对猪蓝湿皮软化效果的影响 ,其软化效果以软化液中羟脯氨酸的浓度增量来表征。研究结果表明 :通过蓝湿皮软化来改善成品革的质量是可行的 ,而且有明显的效果 ;以软化液中羟脯氨酸的浓度来表征软化效果是一个有效的方法 ;当用该复合酶软化猪蓝湿皮时 ,最适 p H值范围为 6 .0 - 6 .5 ;反应温度在 4 0 - 6 5℃之间时 ,软化效果随温度的升高而增大 ;在 5 5℃条件下 ,该酶有很好的热稳定性 ,能长时间保持活力不衰减 ;最适酶用量为 30 0 U/ g试样 ;蓝湿皮的铬含量对软化效果有影响 ,用该方法处理的蓝湿皮 ,其铬离子质量含量一般应≤ 2 .5 %。     

Preparation and photochromism of nanocomposite thin film based on polyoxometalate and polyethyleneglycol

A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism.     

Residual toughness of poly(acrylonitrile-butadiene-styrene) (ABS) after fatigue loading—effect of uniaxial fatigue loading

Toughness variation of non-notched poly(acrylonitrile-butadiene-styrene) (ABS) subjected to uniaxial fatigue loading was investigated. The experiments were conducted by applying fatigue loading to strip specimens first, from which dog-bone specimens were machined. The dog-bone specimens were tested to measure the strain for the on-set of fracture, named cracking strain here, thus to monitor the toughness change due to the fatigue loading.The test results showed that the fatigue loading caused the toughness drop in ABS, even before any visible crack was developed. Damage development and fracture behavior were then analyzed using scanning electron microscopy (SEM). The SEM analysis revealed that damage zones, not cracks, were initiated during the fatigue loading, and were the main cause of the toughness drop. Mechanisms for the damage initiation include matrix crazing and debonding of small rubber particles; however, large rubber particles remained intact. Based on the results, a deformation model is proposed for the damage zone initiation, which provides an explanation for the toughness change under the fatigue loading.     

螺栓角钢钢节点的三维非线性有限元分析

对螺栓角钢钢节点半刚性连接采用非线性有限元分析方法 ,对连接中的主要构件的顶部、底部、腹板角钢、高强螺栓、梁翼缘、柱翼缘和柱翼缘加劲肋进行三维非线性有限元精细模拟 ,针对有无柱加劲肋、有无腹板角钢等几种连接的情况进行比较分析 ,探讨了螺栓角钢半刚性连接的受力性能。