尺寸诱导的聚合物亚稳结晶

亚稳定性是凝聚态物质的一个重要特征。常温常压下，热力学上不稳定的、而实际上存在的相，都可称之为亚稳相。通常，影响物质亚稳态存在的外界因素有温度、压力、电场、磁场等等，而相态本身的大小也是决定它稳性的一个重要因素，这就是所谓的尺寸效应。随着纳米技术和微处理器技术的飞速发展，材料的应用尺寸日趋于小型化和微型化。研究聚合物相行为和相变中的尺寸效应，对于充分理解高分子凝聚态物理学的基本问题具有极度其重要的科学意义，它还为纳米科技中材料特殊的结构和性能提供新的认识途径和理论基础，这必将极度大地促进纳米材料的实用化进程。本文正是基于这样一种相变中的尺寸效应，选用了三种具有多晶型结构的结晶聚合物，聚偏氟乙烯（PVDF），聚反式1,4-丁二烯（TPBD）和尼龙1010（nylon 1010），对它们的晶体结构及其相转变过程和转变条件作了较详细的研究，着重探讨了各种晶型稳态和亚稳态的存在条件。在这三种聚合物当中，发现小尺寸晶体趋向于形成二维高有序的六方或拟六方堆积结构，成功地证明了晶体结构对尺寸的依赖性。在上述研究中，首次成功地为PVDF营造了不同程度的空间受限结晶环境，得到了尺寸小于100纳米受限结晶的亚稳态β晶；通过结合使用常温和低温的电子衍射术，并利用计算机模拟技术，提出了尺寸影响的TPBD相转变的具体实现过程；发现了培养尼龙1010单晶的另一理想溶剂二甲基甲酰胺（DMF），并首次用它培养出十分完善的单晶体；引入尺寸效应的观点来解释尼龙1010的Brill转变现象，定量地确定了基转变温度对尺寸的依赖关系，为解释这一古老但至仿仍存在极大争议的尼龙中特有的转变现象开辟了创造性的思维方式；首次用极度稀溶液喷雾法获得了尼龙1010的纳米和微米级微纤维晶，并解释了它的形成原因。

稳定可调谐的单纵模多环形腔掺铒光纤激光器

提出了一种多环形腔(MRC)结构的稳定可调的单纵模(SLM)掺铒光纤激光器,多环形腔结构由双环形有源腔和两个次级无源腔组成。这种激光器是利用光纤法布里-珀罗可调滤波器(FFP-TF)以及光学光栅滤波器(OGF)两种滤波器和多环形腔结构相结合来共同选模。可实现波长调节范围为1528～1565 nm,在整个波长调节范围内边模抑制比大于44.53 dB,在1554 nm附近边模抑制比可以达到最大值51.18 dB, 输出功率为-8.84 dBm,通过应用多环型腔结构,激光器的输出很稳定,在18 min的观察时间内,中心波长的变化小于0.02 nm,输出功率的变化小于0.04 dBm,实现了稳定且可调谐的单纵模输出。

采用单步光刻和湿法腐蚀工艺制作高性能衍射微透镜

采用单步光刻和湿法腐蚀工艺,低成本快速制作面向高性能蓝光和红光DVD光学头物镜的衍射微透镜.所制微光学结构的表面粗糙度在纳米量级,衍射相位台阶的高度在亚微米量级并可以根据需求灵活调整,通光孔径在毫米至厘米量级的范围内可调.组成衍射微透镜的大量基本相位结构,可以根据入射和出射光束的形貌特征及参数指标,通过衍射积分算法灵活设置和排布.远场光学测试显示了所制衍射微透镜的高衍射效能.

Homoepitaxial Growth and Characterization of 4H-SiC Epilayers by Low-Pressure Hot-Wall Chemical Vapor Deposition

Horizontal air-cooled low-pressure hot-wall CVD (LP-HWCVD) system is developed to get highly qualitical 4H-SiC epilayers.Homoepitaxial growth of 4H-SiC on off-oriented Si-face (0001) 4H-SiC substrates is performed at 1500℃ with a pressure of 1.3×103Pa by using the step-controlled epitaxy.The growth rate is controlled to be about 1.0μm/h.The surface morphologies and structural and optical properties of 4H-SiC epilayers are characterized with Nomarski optical microscope,atomic force microscopy (AFM),X-ray diffraction,Raman scattering,and low temperature photoluminescence (LTPL).N-type 4H-SiC epilayers are obtained by in-situ doping of NH3 with the flow rate ranging from 0.1 to 3sccm.SiC p-n junctions are obtained on these epitaxial layers and their electrical and optical characteristics are presented.The obtained p-n junction diodes can be operated at the temperature up to 400℃,which provides a potential for high-temperature applications.

Fabrication of Novel Superhydrophobic Surfaces and Water Droplet Bouncing Behavior - Part 1: Stable ZnO-PDMS Superhydrophobic Surface with Low Hysteresis Constructed Using ZnO Nanoparticles

A superhydrophobic surface has many advantages in micro/nanomechanical applications, such as low adhesion, low friction and high restitution coefficient, etc. In this paper, we introduce a novel and simple route to fabricate superhydrophobic surfaces using ZnO nanocrystals. First, tetrapod-like ZnO nanocrystals were prepared via a one-step, direct chemical vapor deposition (CVD) approach. The nanostructured ZnO material was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) and the surface functionalized by aminopropyltriethoxysilane (APS) was found to be hydrophobic. Then the superhydrophobic surface was constructed by depositing uniformly ZnO hydrophobic nanoparticles (HNPs) on the Poly(dimethylsiloxane) (PDMS) film substrate. Water wettability study revealed a contact angle of 155.4 +/- 2 degrees for the superhydrophobic surface while about 110 degrees for pure smooth PDMS films. The hysteresis was quite low, only 3.1 +/- 0.3 degrees. Microscopic observations showed that the surface was covered by micro- and nano-scale ZnO particles. Compared to other approaches, this method is rather convenient and can be used to obtain a large area superhydrophobic surface. The high contact angle and low hysteresis could be attributed to the micro/nano structures of ZnO material; besides, the superhydrophobic property of the as-constructed ZnO-PDMS surface could be maintained for at least 6 months. (C) Koninklijke Brill NV, Leiden, 2010

The Effects of Roughness on Adhesion Hysteresis

Adhesion hysteresis is defined as the difference between the work needed to separate two surfaces and that originally gained on bringing them together. Adhesion hysteresis is a common phenomenon in most surface/interface interactions. This paper studies the effects of surface roughness on adhesion hysteresis. We assumed that the surface asperity height distribution is Gaussian. Numerical simulations based on Fuller's model showed that adhesion hysteresis depended upon a single dimensionless parameter, the adhesion parameter, which represents the statistical average of a competition between the compressive forces exerted by the higher asperities, which are trying to separate the surfaces, and the adhesion forces of the lower asperities which are trying to hold the surfaces together. (C) Koninklijke Brill NV, Leiden, 2010

整合素-ICAM-1相互作用的二维反应动力学研究

<正>_2整合素(LFA-1和Mac-1)与其配体细胞间粘附分子-1(ICAM-1)的相互作用在诸如肿瘤转移、炎症反应等许多病理生理过程中起着重要的作用。研究表明,中性粒细胞(PMN)在特定环境下可通过_2整合素与ICAM-1的相互作用而增强黑色素瘤细胞的转移能力,但是其动力学调控机制还不清楚。受体-配体键结合和解离的二维反应动力学定量描述了分子结合的快慢和强弱,是回答_2整合素与ICAM-1相互作用如何调

~(12)C~(6+)离子辐射对细胞存活增殖及模拟失重和辐射对家蚕卵发育的影响

目的:观察重离子辐射后人骨肉瘤细胞MG-63、人胚胎皮肤成纤维细胞ESF-1和人胚胎肝正常细胞HEL-1的生存和增殖情况,及重离子辐射和模拟失重环境处理后家蚕卵的孵化和发育情况,初步探讨重离子辐射对细胞及复合环境对家蚕卵的一些生物学效应.方法:利用超导磁体模拟失重环境,利用重离子加速器产生12C6+离子,用不同剂量辐射细胞和家蚕卵,检测在重离子辐射后细胞的存活和克隆形成能力及复合条件下家蚕卵的发育情况.结果:HEL-1细胞在0.1Gy时存活率已经开始降低,且随辐射剂量的增大这种影响也增加,到1.5Gy时存活率降低50%.ESF-1细胞在1.5Gy时存活率下降约20%,但辐射对骨肉瘤MG-63细胞的存活率影响不大.HEL-1和ESF-1细胞受到0.1Gy的辐射后克隆形成能力就明显降低90.2%和79.1%,而MG-63细胞一直保持较高的克隆形成率,直到1.5Gy时迅速降低75%.家蚕的出蚁率随辐射剂量的增大而降低,到30Gy时出蚁率降到2.22%.当辐射剂量为0～10Gy时,家蚕卵在两种不同重力条件下的孵化率没有明显差异.但当辐射剂量增加到15,20和30Gy时,失重环境明显促进了家蚕卵的孵化.另外,失重环境下家蚕卵的孵化时间比正常条件下缩短约3d左右.同时,高剂量的辐射处理会延迟家蚕幼虫的生长.结论:重离子辐射降低了细胞的存活和增殖能力,同时影响了家蚕从受精卵到幼虫的发育,降低了出蚁率.失重环境可以缩短家蚕卵的孵化时间.