Passively mode-locking Nd : Gd0.5Y0.5VO4 laser with an In(0.25)Ga(0.75)Aa absorber grown at low temperature

We have demonstrated stable self-starting passive mode locking in a diode-end-pumped Nd:Gd-0.8-Y0.5VO4 laser by using an In0.25Ga0.75As absorber grown at low temperature (LT In0.25Ga0.75As absorber). An In0.25Ga0.75As single-quantum-well absorber, which was grown directly on the GaAs buffer by use of the metal-organic chemical-vapor deposition technique, acts simultaneously as a passive mode-locking device and as an output coupler. Continuous-wave mode-locked pulses were obtained at 1063.5 nm. We achieved a pulse duration of 2.6 ps and an average output power of 2.15 W at a repetition rate of 96.4 MHz. (c) 2005 Optical Society of America.

P(AA-DAC)两性聚电解质水凝胶的合成及性质

以丙烯酸(AA)和丙烯酰氧乙基三甲基氯化铵(DAC)为单体,采用水溶液聚合法制备了P(AA-DAC)聚电解质水凝胶.采用红外光谱和核磁共振等方法对其结构进行了表征.研究了不同组成比的聚电解质水凝胶在去离子水、不同pH值溶液以及不同离子强度盐溶液中的溶胀行为

PP-g-AA接枝共聚物的制备及表征

以部分预辐照聚丙烯(rPP)作为聚丙烯反应挤出接枝丙烯酸(AA)的引发剂,制备了PP-g-AA接枝共聚物。考察了预辐照剂量、预辐照聚丙烯用量以及单体浓度等因素对接枝反应的影响。采用红外光谱、差热扫描量热仪和偏光显微镜等测试技术对接枝产物的形态、结构及性能进行了研究。结果表明,这种新的PP-g-AA共聚物制备方法能有效抑制聚丙烯的降解并获得较高力学性能的接枝产物。研究发现,当rPP的预辐照剂量为4 kGy,反应原料的组成为m(PP)∶m(rPP)∶m(AA)=90∶10∶0.8时,得到的产物有较高的接枝率(0.19%),并且具有相对最佳的力学性能;这种接枝产物与铝板有很强的粘接效果,其剥离强度达4.88 kN/m。

LLDPE-g-AA的流变行为及力学性能

利用毛细管流变仪研究了线性低密度聚乙烯接枝丙烯酸 (LLDPE - g -AA)的流变行为。结果表明 ,在高的剪切应力下LLDPE -g -AA的表观粘度比纯LLDPE的小 ,并改进了树脂的流动性和加工性。LLDPE - g -AA的表观粘度随接枝丙烯酸含量的增加而降低 ,说明接枝到LLDPE分子链上的丙烯酸起到了内润滑剂的作用。利用Instron 112 1拉力机测试了LLDPE - g -AA的力学性能 ,结果表明其拉伸强度、杨氏模量和断裂伸长率与纯LLDPE相比没有明显的变化

LLDPE/LLDPE-g-AA共混物的接触角及红外光谱表征

利用熔融共混的方法制备了线性低密度聚乙烯/线性低密度聚乙烯接枝丙烯酸(LLDPE/LLDPE-g-AA)共混物。用傅里叶红外光谱(FT-IR)和测定接触角的方法对不同LLDPE-g-AA含量的LLDPE/LLDPE-g-AA共混物膜的表面进行了表征。结果表明,随着共混物中LLDPE-g- AA含量的增加,水和甘油等极性液体与共混物表面的接触角下降。依据共混物的FT-IR计算了其羧基峰强度。发现极性液体与LLDPE/LLDPE-g- AA共混物膜表面的接触角越小,羧基峰强度越大。

Interaction characterization of PA1010/PP blends using PP-g-AA as compatibilizer

The morphology of polyamidelOlO/polypropylene blends was found to significantly depend upon the concentration of the compatibilizer[polypropylene-grafted-acrylic acid (PP-g-AA)]. A significant reduction in phase size was observed because of the interaction that existed between the PP-g-AA and polyamide. These interactions have been confirmed by several methods. The tensile mechanical properties and impact behavior of the prepared blends were investigated and correlated with scanning electron microscope (SEM) analysis of the fracture surfaces. It was found that PP-g-AA as the compatibilizer has a profound effect upon the properties of the blends. This behavior is attributed to a series of chemical and physico-chemical interactions taking place between the two components.

PP－g－AA的制备和表征

用熔融接枝方法制备了聚丙烯－ｇ－丙烯酸（ＰＰ－ｇ－ＡＡ）。用光电子能谱，广角Ｘ射线衍射，红外光谱和化学滴定方法对接枝物进行了定性和定量表征。讨论了单体和引发剂浓度对接枝率的影响，确定了用红外光谱法测定接枝物含量的经验公式

THE CHAIN STRUCTURE AND LIGHT-SCATTERING-STUDIES FOR ACRYLAMIDE-SODIUM ACRYLIC-ACID (AM-AA) COPOLYMERS

A set of AM-AA copolymer samples with the same comonomer content and different average molecular weight have been characterized by C-13 NMB and light scattering methods in this paper. The chemical composition (comonomer AA, mole content 16.9 +/- 1.1%) of these samples is uniform. the sequence of AA in the macromolecular chain is of alone and random distribution and the light scattering theory from polyelectrolyte in added-salt solutions is suitable for the AM-AA copolymers-0.12 mol/L NaCl water systems. The actual values of M(w), the second Virial coefficient A(2) and the mean square radius of gyration (R(2)), for the studied samples have been obtained. The relationships between the molecular parameters are as follows: A(2)=0.0619 ($) over bar M(w)(-0.24), < R(2) >(1/2)(t)= 0.0210 ($) over bar M(w)(0.54).

表面应力调制的微流控技术的驱动原理

发展和优化对薄膜、液滴和气泡进行流动控制操作的多功能装置,要求深入了解界面现象和微流体动力学流动.表面积/体积的大比值和低雷诺数流动是此类系统的特点.毛细数和Bond数强烈地受边界效应影响,因而可以通过各种表面处理和表面力来进行控制.本文综述了运用调制法向或切向应力,对均匀的、带化学处理条纹及拓扑结构纹理表面上的微滴和液膜进行驱动的常用技术的基本原理.

吸湿特性对胶体颗粒自组装过程的影响

光子晶体的独特性质使得人们有可能实现对光子的操控，从而实现电子时代向光子时代的转变。光子晶体最重要的两个因素是周期性和构成周期性的材料的介电常数差。光子晶体的制备方法有很多种，胶体晶体模板法在制备成本和效率上具有明显的优势，因而得到研究者的重视。而在胶体晶体干燥过程中产生的裂纹破坏了胶体晶体的周期性，从而制约了这种方法在光子晶体制备方面的应用。 本文从如何利用微球吸湿性来研究胶体晶体自组装过程中裂纹的影响。主要从两个方面来进行研究：微球的表面吸湿改性及改变衬底的吸湿性。利用乳液聚合法获得了单分散性好的、不同粒径的聚苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球。系统地考察了软硬单体配比、丙烯酸用量、乳化剂和引发剂的用量对微球的粒径和形态的影响。利用垂直生长法生长聚苯乙烯/丙烯酸正丁酯/丙烯酸Poly（St-BA-AA）微球薄膜，通过改变外界湿度条件，测得薄膜的反射光谱，得到Poly（St-BA-AA）的吸湿性结论。同时结合测得的微球的傅里叶变换红外光谱，即FITR谱图结果，得出聚苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球的特殊性能以及新的应用前景。 本文还从改变衬底的吸湿性出发，提出通过利用微球的吸湿特性来采用与胶体微球“同胀同缩”衬底来影响裂纹的形成的原理，制备了一系列的吸湿性材料及其薄膜，包括聚丙烯酸钠薄膜、含聚甲基丙烯酸甲酯（PMMA）和高吸水树脂薄膜、含双丙酮丙烯酰胺（DAAM）的水性涂料薄膜、含DAAM苯丙乳液薄膜。讨论了这些材料的吸水性能及成膜性能的影响因素。然后，以含DAAM的水性涂料薄膜及含DAAM苯丙乳液薄膜作为衬底，控制生长环境温度为55℃、相对湿度为30%，利用垂直生长法制备聚苯乙烯（PS）胶体晶体。利用光镜照片分析了吸水性衬底对薄膜裂纹情况的影响，从机理上分析了裂纹产生的原因，同时这种方法还为系统地研究吸水性衬底对胶体晶体生长过程中产生的裂纹的影响提供了新的思路。

Gamma-ray induced color centers in Yb : YAG crystals grown by Czochralski method

20 at.% Yb:YAG single crystals have been grown by the CZ method and gamma-ray irradiation induced color centers and valence change of Fe3+ and Yb3+ ions in Yb:YAG have been studied. One significant 255 nm absorption band was observed in as-grown crystals and was attributed to Fe3+ ions. Two additional absorption (AA) bands located at 255 nm and 345 nm, respectively, were produced after gamma irradiation. The changes in the AA spectra after gamma irradiation and air annealing are mainly related to the charge exchange of the Fe3+, Fe2+, oxygen vacancies and F-type color centers. Analysis shows that the broad AA band is associated with Fe2+ ions and F-type color centers. The transition Yb3+ Yb2+ takes place as an effect of recharging of one of the Yb3+ ions from a pair in the process of gamma irradiation. (C) 2006 Elsevier Ltd. All rights reserved.

Defects in U3+: CaF2 single crystals grown under different conditions by the temperature gradient technique

Defects in as-grown U3+ : CaF2 crystals grown with or without PbF2 as an oxygen scavenger were studied using Raman spectra, thermoluminescence glow curves, and additional absorption (AA) spectra induced by heating and gamma-irradiation. The effects of heating and irradiation on as-grown U3+: CaF2 crystals are similar, accompanied by the elimination of H-type centers and production of F-type centers. U3+ is demonstrated to act as an electron donor in the CaF2 lattice, which is oxidized to the tetravalent form by thermal activation or gamma-irradiation. In the absence of PbF(2)as an oxygen scavenger, the as-grown U3+:CaF2 crystals contain many more lattice defects in terms of both quantity and type, due to the presence of O2- impurities. Some of these defects can recombine with each other in the process of heating and gamma-irradiation. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.