HDPE／LLDPE共混物高取向薄膜微结构电子显微学研究

本工作用透射电镜(TEM)、电子衍射和示差扫描量热计(DSC)等方法研究高密度聚乙烯(HDPE)和线性低密度聚乙烯(LLDPE)共混物高取向薄膜的微结构。结果表明熔体拉伸HDPE/LLDPE共混物薄膜含有高取向片晶结构。随着共混物中LLDPE含量的增加,片晶的尺寸相应减小。当LLDPE含量超过50％时,结晶结构从纯HDPE的非对称性纤维结构变为对称性纤维结构。高取向共混物在全组成范围成内形成共结晶。     

PVF2／PMMA共混物薄膜的电子显微学研究

聚甲基丙烯酸甲酯(PMMA)是少数与聚偏氟乙烯(PVF_2)热力学相容的聚合物之一。对于PVF2/PMMA共混体系相容性的研究较为广泛,但对其晶相结构的研究却少见报道。本工作采用特殊的熔体拉伸方法制备高取向PVF_2/PMMA共混物薄膜,并用透射电子显微镜(TEM)和富里叶变换红外光谱(FTIR)等方法研究了PMMA对高取向PVF_2薄膜形态结构的影响。 TEM结果表明,在熔体拉伸的PVF_2薄膜中,含有高度取向的片晶结构,其生长方向垂直与拉伸方向。而在PVF_2/PMMA共混物薄膜中除PVF_2片晶外,还出现了与拉伸方向平行的纤维晶,纤维晶的数量随PMMA分子量的提高而增多。     

熔体浇铸的聚丙烯／高密度聚乙烯共混薄膜的形态结构

本文的研究对象是高密度聚乙烯(HDPE)和聚丙烯的熔体共混物,其中聚乙烯的重量百分数分别为0,1,2,3,5和10,文中叙述了熔体浇铸薄膜的制备方法和用TEM对它们进行的形态研究。当HDPE含量为10％或5％时,共混体系分离成两相。HDPE相的微区尺寸为3000(?)～800(?),微区由一些片晶组成。从我们的实验中可以认为共混物中HDPE的临界浓度应小于5％,而且在熔体中PP和HDPE之间存在一些弱的相互作用。     

用于全介质自承式光缆的新一代聚乙烯化合物

聚乙烯(PE)在电线电缆中用作护套材料已有很长的历史。前几年一直广泛采用传统的高压低密度聚乙烯(LDPE)，但现在已被线性材料大量取代。这些聚乙烯——线性低密度聚乙烯(LLDPE)、中密度聚乙烯(MDPE)和高密度聚乙烯(HDPE)——均具有优于LDPE和PVC的机械性能和物理性能。以丹麦Borealis的专利技术Borstar为基础研制出的双峰材料，为具有改进性能的新一代护套材料开辟了道路，这些材料对于电缆的生产、安装和使用寿命来说十分重要。     

不同种类聚乙烯取向态结晶结构研究

本工作是用电子显微镜研究三种PE(HDPE、LLDPE和LDPE)高取向超薄膜的结晶结构。不同种类PE高取向超薄膜以特殊的熔体拉伸方法制备。该方法的特点是以较低的拉伸速率(4cm/Sec)在很窄的熔体流动区域内(0.5—1.0μm),获得非常高的纵向流动梯度(4×10~4/Sec)和过冷速率。所得超薄膜厚度为50-100nm,可直接用TEM观察。所用电镜为H-600型,操作电压为100KV。明场像采用欠焦成像技术。并利用电子显微镜的多功能,诸如衍射、明场、暗场、样品旋转及倾斜等严格确定了三种PE熔体拉伸膜取向态的晶体结构。     

聚丙烯/乙丙橡胶共混物熔体拉伸薄膜的形态结构研究

本工作是用电子显微镜研究以特殊的熔体拉伸方法制备高取向PP/乙丙橡胶(EPDM)共混物超薄膜的形态结构及其相容性。不同组成PP/EPDM共混物(EPDM重量百分含量为5—50％)高取向超薄膜以特殊的熔体拉伸方法制备。该方法的特点是在小的熔体流动区域内(0.5—1.0μm),以较低的拉伸速率(4cm/sec)获得非常高     

用膨胀挤压法制造泡沫高密度聚乙烯绝缘电线

1.绪言泡沫聚乙烯是以改善电信电缆的电气特性和降低电缆成本为目标,作为绝缘体而被广泛使用。可是现在用挤压法制造的泡沫聚乙烯基本上都是低密度聚乙烯(以下简称 LDPE),高密度聚乙烯(以下简称HDPE)却很少,特别是导体用细线,加工线速快的场合,使用HDPE 制造泡沫 HDPE 绝缘可以说是不大可能的。     

HDPE在单轴取向iPP膜上的附生结晶

最近,聚合物之间的附生结晶引起人们的关注,其中较多工作集中在聚乙烯/聚丙烯共混或复合体系。原因是附生结晶不但具有特殊的形态结构,而且对材料的力学性能有重要的影响。附生结晶是一种结晶物质在另一种结晶物质上的附生生长,二者之间有的特殊作用。两种结晶聚合物之间的相互作用非常复杂,其中的结构关系不象聚合物在有机或无机基质上的附生关系那么简单。电子显微镜是研究结晶材料中附生结晶的有力工具。本工作用电子显微镜方法研究了熔体拉伸薄膜中高密度聚乙烯(HDPE)在高取向聚丙烯(ipp)上的附生结晶。     

改性聚丙烯的形态研究

大宗生产的通用型塑料聚丙烯(PP),具有许多优良性质。但是它的低温脆性。限制了更广泛的应用。因此,通过各种增韧剂改性PP,以克服PP的低温脆性,是各国塑料加工应用研究工作者为之多年努力的目标。本文作者通过透射电镜(TEM)和偏光显微镜观察与研究改性PP的形态及其增韧机理。低密度聚乙烯(LDPE)和高密度聚乙烯(HDPE)与PP共混时,用偏光显微镜可清楚地观察到PP的球形结晶变小了。并且随着聚乙烯(PE)加入量的增加,结晶花纹愈来愈变得模糊不清。从TEM照片(照片1),可清楚地观察到PE作为分散相仿佛是球形岛屿分布于PP组成的海中。PE的增韧作用源     

聚乙烯化学染色及其结晶形态TEM研究

自Konig发表了结晶聚乙烯染色方法以来,以TEM为手段研究结晶聚乙烯的微观结构形态的工作有了突飞进展,为建立块状聚乙烯片晶堆积(聚集态)模型提供了有力的直观依据。在konig工作的启发下,近年来又相继成功地找到了适于聚酯类高巨物,共巨、共混及接技高巨物的染色方法,进而扩大了以TEM为手段,深入研究高巨物形态结构的路子。     

Single‐Molecule Tracking of Fibrinogen Dynamics on Nanostructured Poly(ethylene) Films

Using fibrinogen (Fg) protein as a probe molecule, mapping using accumulated probe trajectories (MAPT) is performed on nanostructured melt‐drawn high‐density poly(ethylene) (HDPE) films composed of well‐oriented crystalline patches separated by amorphous regions. The spatially grouped molecular trajectories allow for identification of regions with distinct surface properties (i.e., crystalline vs. amorphous) while simultaneously determining the characteristic dynamic protein behavior within those regions. In the presence of solution with a sufficiently high Fg concentration, discrete patches of a dense, ordered protein layer form (presumably on crystalline HDPE regions), leading to a dramatic rise in the surface residence time (by more than two orders of magnitude) of molecules incorporated into the film. Within this ordered Fg layer, individual molecules exhibit slow anisotropic lateral diffusion; the mobility is restricted by the nanostructure boundaries of the underlying HDPE. On HDPE films at low Fg surface coverage, or on films that have been rendered hydrophilic with Ar plasma, short surface residence times and fast, isotropic diffusion are observed. These results demonstrate the ability of spatially resolved single‐molecule tracking to provide mechanistic information about biomolecule‐surface interactions in a highly heterogeneous environment.     

Controlling the Degree of Crystallinity and Preferred Crystallographic Orientation in Poly‐Perfluorodecylacrylate Thin Films by Initiated Chemical Vapor Deposition

Preferred crystallographic orientation (texture) in thin films of technologically important materials frequently has a strong effect on the properties of these films and is important for stable surface properties. The deposition of organized molecular films of a poly‐perfluorodecylacrylate, poly‐(1H,1H,2H,2H‐perfluorodecyl acrylate) (p‐PFDA), by initiated chemical vapor deposition (iCVD) is described. The tendency of p‐PFDA to crystallize in a smectic B phase has been reported in films prepared from solution but not for those using a CVD technique. The degree of crystallinity and the preferred orientation of the perfluoro side chains, either parallel or perpendicular to the surface, are controlled by tuning the CVD process parameters (i.e., initiator to monomer flow rate ratio, filament temperature, and substrate temperature). Films with no observable X‐ray diffraction patterns are also achieved. The observed differences in crystal texture strongly impact the observed water contact angles (150° to 130°, advancing) and corresponding hysteresis behavior. Low hysteresis (<7°) is associated with high crystallinity, particularly when the orientation of the crystallites resulted in the perfluoro side groups being oriented parallel to the surface. The latter texture resulted in smoother film than the texture with the chains oriented perpendicular to the surface and this can be very advantageous for applications in which relatively smooth but still crystalline films are needed.     

平面应变压缩过程中初始取向对AZ31镁合金变形行为的影响

在室温和150℃下对AZ31镁合金进行平面应变压缩试验,应变速率为0.01 s-1,形变量为0.1.试样(切割于强织构的热轧板)的压缩轴c与其基面法向成不同的角度,从而研究初始织构对AZ31镁合金塑性变形行为的影响.利用电子背散射衍射花样(EBSD)采集变形试样的微观结构和织构信息,分析孪生和滑移行为.实验发现AZ31镁合金塑性变形由{10(-12)}<(-10)11>拉伸孪生和基面滑移共同控制,并确定了各种变形模式比例与晶体初始取向的关系,其中拉伸孪生在压缩轴垂直于c轴方向时占主导作用.     

A Versatile Method to Fabricate Highly In‐Plane Aligned Conducting Polymer Films with Anisotropic Charge Transport and Thermoelectric Properties: The Key Role of Alkyl Side Chain Layers on the Doping Mechanism

A general method is proposed to produce oriented and highly crystalline conducting polymer layers. It combines the controlled orientation/crystallization of polymer films by high‐temperature rubbing with a soft‐doping method based on spin‐coating a solution of dopants in an orthogonal solvent. Doping rubbed films of regioregular poly(3‐alkylthiophene)s and poly(2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b ]thiophene) with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄TCNQ) yields highly oriented conducting polymer films that display polarized UV–visible–near‐infrared (NIR) absorption, anisotropy in charge transport, and thermoelectric properties. Transmission electron microscopy and polarized UV–vis–NIR spectroscopy help understand and clarify the structure of the films and the doping mechanism. F₄TCNQ^? anions are incorporated into the layers of side chains and orient with their long molecular axis perpendicular to the polymer chains. The ordering of dopant molecules depends closely on the length and packing of the alkyl side chains. Increasing the dopant concentration results in a continuous variation of unit cell parameters of the doped phase. The high orientation results in anisotropic charge conductivity (σ) and thermoelectric properties that are both enhanced in the direction of the polymer chains (σ = 22 ± 5 S cm^?1 and S = 60 ± 2 µV K^?1). The method of fabrication of such highly oriented conducting polymer films is versatile and is applicable to a large palette of semiconducting polymers.     

溅射法制备ZnO薄膜结构及光学特性

采用直流磁控溅射镀膜工艺在玻璃基片上沉积了具有良好c轴择优取向的znO薄膜.用组合式多功能光栅光谱仪测得透光率均在85%以上;用AXRF分析了退火前后薄膜的物相,并用原子力显微镜分析了薄膜的表面形貌.样品通过空气中退火,薄膜结晶质量明显提高,晶粒有所长大,取向更加一致.在室温下用荧光分光光度计分析了薄膜的发光特性,观测到明显的紫外光发射(波长为386 nm)和波峰为528nm的一"绿带"宽峰.紫外发射是由于导带和价带之间的电子跃迁,宽峰是源于晶体的缺陷.     

Engineering of Graphene Layer Orientation to Attain High Rate Capability and Anisotropic Properties in Li‐Ion Battery Electrodes

Novel carbon films with different graphene layer orientations are investigated as electrode materials for Li‐ion batteries. It is demonstrated that engineering the crystallographic orientation with graphene layers oriented perpendicular to the surface substantially alters stress evolution during Li insertion. With this crystallographic orientation the intercalating/de‐intercalating Li‐ions also have direct access to the graphene interlayer spaces, resulting in higher capacity at faster electrochemical cycling, compared to carbon films with graphene layers parallel to the film surface. Electrodes with perpendicular alignment are prepared by supramolecular synthesis using either spin coating or bar coating of chromonic liquid crystal precursors into precursor organic films followed by in situ carbonization. These materials are compared with in situ stress measurements during lithiation/delithiation cycles, and the bar‐coated films exhibit a highly anisotropic stress which is consistent with long‐range alignment of the graphene layers. In contrast, the in‐plane stresses in the spin‐coated films are isotropic, which is consistent with the presence of randomly oriented domains (still with graphene layers oriented perpendicular to the surface). Overall, the use of thin film graphitic materials with controlled crystallographic orientations provides a valuable platform for investigating the impact of graphene structure on the properties of Li‐ion battery electrode materials.     

氩气压强对溅射法制备Ga掺杂ZnO薄膜性能的影响

采用射频磁控溅射法在玻璃衬底上制备了高质量的Ga掺杂ZnO透明导电薄膜(GZO).通过X射线衍射、原子力显微镜、四探针电导率测试仪等表征方法研究了溅射气压对薄膜结晶特性及导电性能的影响.所制备的GZO薄膜是具有六角纤锌矿结构的多晶薄膜,最佳择优取向为(002)方向.随着溅射气压的增大,薄膜方块电阻与薄膜电阻率均随之增大.最小方块电阻可达17.6 Ω/□,最小薄膜电阻率为7.3×10~(-4) Ω·cm.另外,GZO薄膜在可见光范围内的透过率达到了90%以上.     

PLD法制备高介电调谐率的纳米晶BZT薄膜

用脉冲激光沉积工艺制备了Ba(ZrxTi1-x)O3(x=0.25,0.30简称BZT25和BZT30)介电薄膜。在650℃原位退火10 min,薄膜为(111)取向柱状生长的晶粒,取向度分别为0.45和0.75。BZT25和BZT30薄膜的平均晶粒尺寸分别为50 nm和60 nm。在室温、1 MHz和3×105 V/cm条件下,BZT25的最大εr和调谐率分别达到563和65%,BZT30的最大εr和调谐率分别达到441和57%。薄膜为(111)取向生长,主要是基于薄膜与底电极Pt界面层立方相结构Pt3Ti的诱导,即(111)Pt3Ti和(111)BZT的晶格匹配。     

高度(100)取向的BST薄膜及其高介电调谐率

用脉冲激光沉积法制备(Ba1-xSrx)TiO3(x=0.35,0.50简称BST35和BST50)介电薄膜。在650℃原位退火10min,获得高度(100)取向柱状生长的晶粒。BST35薄膜的平均晶粒尺寸为50nm,BST50薄膜的晶粒尺寸为150~200nm。在室温和1MHz条件下,BST35的最大εr和调谐率分别达到810和76%,其介电调谐率高于国内外同类文献报道的数据;BST50的εr和调谐率最大分别达到875和63%。薄膜为(100)取向生长,因为薄膜沿平面c轴极化而产生应力,在电场作用下,而获得高介电调谐率。     

电化学方法生长有序纳米柱阵列的发光性质

采用电化学方法在磁控溅射方法生长的ZnO薄膜上生长垂直于衬底排列的ZnO纳米柱.ZnO薄膜的作用主要是为ZnO纳米柱的生长提供同质外延层.电化学生长的ZnO纳米柱具有良好的晶体质量和发光性能.通过研究其变温发光光谱可以确定其紫外发光峰来自于带边激子的辐射复合.此种方法生长的ZnO纳米柱在场发射显示、蓝紫色和白光发光二极管方面有潜在的应用前景.