辐照聚乙烯单晶的退火研究

用红外光谱、ＤＳＣ、ＳＡＸＳ和ＷＡＸＤ等方法考察了辐照５ＭＧｙ后的聚乙烯单晶在退火前后的结构变化，对比未辐照样品在同样条件下的变化，提出在９０℃以下和１０５℃聚乙烯有不同的退火机理，辐照引起的交联和晶区结构损伤，限制了退火对晶体结构的改善程度．     

溶剂蒸汽退火法制备有机小分子半导体单晶

溶剂蒸汽退火(Solvent Vapor Annealing, SVA)是一种经济高效的小分子半导体晶体生长制备方法. 本工作通过该方法制备出了多种小分子有机半导体单晶, 通过偏光显微镜, XRD, TEM 和 AFM对得到的单晶的形貌和晶体结构进行了表征. 此外, 我们对退火所用溶剂的溶解度、蒸汽退火的环境温度和聚合物介质的引入等影响因素进行了讨论. 研究发现, SVA过程中随着退火溶剂对有机半导体的溶解度增大, 得到的晶体尺寸也随之增大; 此外, 当退火温度升高, 晶体生长速度加快, 但当温度接近溶剂蒸汽的沸点时, 晶体极易产生缺陷; 聚合物的引入可以大大促进SVA进程, 并且生长得到的有机半导体单晶缺陷更少, 尺寸更大.     

超高分子量聚乙烯的红外光谱的特性研究

研究了超高分子量聚乙烯(M_w>1×10⁵)的红外光谱-温度特性.3条非晶谱带(1368、1352和1304cm^-1)的吸收强度均随温度升高而增大,但都比普通分子量聚乙烯增加的小,尤以高于140℃更甚.分子链中次甲基的近程构象序列分布随温度的变化不受分子量的影响,但旁式构象序列分布则随温度升高而增大.升温和降温过程的红外光谱均表明1352和1304cm^-1两谱带随结晶状态的变化比1368cm^-1更敏感.     

氯磺化聚乙烯的γ—辐射交联

氯磺化聚乙烯(简称CSM)由于存在SO_2Cl基团很容易通过金属氧化物进行化学交联,但至今未见其辐射交联的详细报道.本文探讨氯含量对CSM辐射交联的影响. 所用CSM系吉林化工公司产品:20型(含氯量29～33％,下同),40型(33～37％)和30型(40～45％).将CSM和防老D按一定比例混炼均匀,再在140℃左右热压成形.试样用3.33×10~(15)Bg ~(60)Co于室温限量空气下进行辐照.辐照过的试样于80℃处理2小时以消除俘陷自由基.在氮气保护下先后用二甲苯和无水乙醇,加热回流48小时和8小时,测定凝胶含量.     

线性低密度聚乙烯/橡胶共混体系的相容性研究

本文用FTIR-ATR方法考察了线性低密度聚乙烯与天然橡胶(NR)及丁苯橡胶(SBR)两个共混体系,发现NR的835cm~(-1)和SBR的964cm~(-1)两个吸收峰因与聚乙烯共混而增高变窄,说明聚乙烯的非晶链段和橡胶分子之间存在一定程度的相互作用。     

铂单晶电极表面不可逆反应动力学──Ⅰ.Pt(100)单晶电极上甲酸氧化的现场红外反射光谱研究

运用电化学暂态方法和现场时间分辨FTIR反射光谱研究甲酸在Pt（100）单晶电极上的解离吸附和氧化过程．深入认识了甲酸解离吸附的反应速率在-0．25至0．25V电位区间呈火山形变化的规律．根据电化学现场时间分辨红外光谱的研究结果，提出在研究反应动力学时避免甲酸解离吸附干扰的方法，为进一步研究甲酸在Pt（100）电极表面经活性中间体直接氧化至CO2的反应动力学奠定了基础．     

正交投影耦合光谱平滑性红外光谱法用于聚乙烯/聚丙烯共混物的定量分析

运用正交投影技术，结合目视背景光谱平滑性，对二元共混物中各组分进行红外光谱定量分析。将该法用于聚乙烯／聚丙烯共混物的实际样品测定，能满足生产控制的要求。     

铂单晶电极表面不可逆反应动力学I.Pt(100)单晶电极上甲酸氧化的现场红外反射光谱研究

运用电化学暂态方法和现场时间分辨ＦＴＩＲ反射光谱研究甲酸在Ｐｔ（１００）单晶电极上的解离吸附和氧化过程,深入认识了甲酸解离吸附的反应速率在－０．２５至０．２５Ｖ电位区间呈火山形变化的规律。根据电化学现场时间分辨红外光谱的研究结果,提出在研究反动力学时避免甲酸解离吸附干扰的方法,为进一步研究甲酸在Ｐｔ（１００）电极表面经活性中间体直接氧化至ＣＯ２的反应动力学奠定了基础。     

固相氯化法合成氯化聚乙烯的红外光谱研究

本文研究在不同条件固相氯化聚乙烯(CPE)的红外光谱,探讨了一步和两步氯化合成的CPE的结构差别,着重讨论了两步氯化的CPE结构特点。从观察表征结晶结构和—(CH_2)_n—链段氯分布的特征频率变化表明,低温固相氯化主要发生在无定形区,并且在CPE中形成高氯化和低氯化链段(或未氯化)的嵌段结构。在两步固相氯化时,晶区受到较大程度的破坏,氯化作用已不局限在无定形区,其结晶结构的破坏主要同第二步氯化程度有关,即使CPE氯含量相同,若前后两步氯化程度不同,结构有很大差异。     

聚乙烯拉伸过程中晶态变化及形变机理

用红外光谱和X-射线衍射研究了室温拉伸的聚乙烯,结果显示单斜晶存在于室温拉伸的聚乙烯中。对Hendra等关于拉伸过程机理的“微熔融”理论及其所根据实验结果提出异议,而本文的,实验结果支持了Peterlin模型。     

Surface Fixing Effect of Vacuum Evaporated Particles on Polyethylene Single Crystals

Summary: The recrystallization behavior of high density polyethylene (HDPE) single crystals with vacuum evaporated metal chromium or carbon on their surface has been investigated by transmission electron microscopy (TEM) and electron diffraction (ED) techniques. The results indicate that the particle‐coated HDPE single crystals can retain their single crystal structure after complete melting and subsequent recrystallization, with the heat‐treated temperature as high as 200 °C. This phenomenon is attributed to a surface fixing effect of vacuum evaporated Cr or carbon on the single crystals.

A bright‐field electron micrograph and the corresponding electron diffraction pattern of recrystallized Cr‐coated HDPE single crystals.     

Functionalizing Single Crystals: Incorporation of Nanoparticles Inside Gel‐Grown Calcite Crystals

Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe₃O₄ nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution‐grown crystals do not. As such, our work extends the long‐history gel method for crystallization into a platform to functionalize single‐crystalline materials.     

Frequency Dependence of the Dynamic Heat Capacity at the Melting Temperature of Polyethylene Crystals

The dynamic heat capacity of polyethylene was measured in the heating process over two decades of the modulating frequency using the light heating modulated temperature DSC. The dynamic heat capacity exhibited clear frequency dependence from 95°C to the end of the melting of the crystals. Frequency dependence of this work was compared with that of the quasi-isothermal measurement. The relaxation time estimated in this work was much shorter than that of the quasi-isothermal measurement. It was found that notable heat exchange between the sample and reference sides occurred between 120 and 135°C. Frequency dependence of the heat exchange was studied.This revised version was published online in November 2005 with corrections to the Cover Date.     

The Effect of Substrate on the Annealing of Poly(butylene succinate) Single Crystals

The morphological evolution of poly(butylene succinate) (PBS) solution‐grown single crystals during annealing was studied using hot‐stage atomic force microscopy. Their morphology changed with increasing temperature and annealing time. The annealing behavior and melting temperature were found to be affected by the substrate. Morphological changes occurred at a much lower temperature on an amorphous carbon film than that on a mica surface. Moreover, the pattern of morphological evolution of the single crystals on a carbon film was different from that on a mica surface. Since the PBS melt had a larger contact angle on the mica surface, these differences in the melting behavior were ascribed to the different interfacial interactions between the chain‐folded surface of the single crystal and the substrate.

     

Dissolution of Platinum Single Crystals in Acidic Medium

Platinum single crystal basal planes consisting of Pt(111), Pt(100), Pt(110) and reference polycrystalline platinum Pt(poly) were subjected to various potentiodynamic and potentiostatic electrochemical treatments in 0.1 M HClO₄. Using the scanning flow cell coupled to an inductively coupled plasma mass spectrometer (SFC-ICP-MS) the transient dissolution was detected on-line. Clear trends in dissolution onset potentials and quantities emerged which can be related to the differences in the crystal plane surface structure energies and coordination. Pt(111) is observed to have a higher dissolution onset potential while the generalized trend in dissolution rates and quantities was found to be Pt(110)>P(100)≈Pt(poly)>Pt(111).     

Visualizing Phase Segregation in Mixed‐Halide Perovskite Single Crystals

Mixed organolead halide perovskites (MOHPs), CH₃NH₃Pb(Br_xI_1?x)₃, have been shown to undergo phase segregation into iodide‐rich domains under illumination, which presents a major challenge to their development for photovoltaic and light‐emitting devices. Recent work suggested that phase‐segregated domains are localized at crystal boundaries, driving investigations into the role of edge structure and the growth of larger crystals with reduced surface area. Herein, a method for growing large (30×30×1 μm³) monocrystalline MAPb(Br_xI_1?x)₃ single crystals is presented. The direct visualization of the growth of nanocluster‐like I‐rich domains throughout the entire crystal revealed that grain boundaries are not required for this transformation. Narrowband fluorescence imaging and time‐resolved spectroscopy provided new insight into the nature of the phase‐segregated domains and the collective impact on the optoelectronic properties.     

γ—射线辐照对聚乙烯单晶结构的影响

采用混合晶红外光谱、X-射线衍射及小角散射、差示扫描量热法研究γ-射线辐照对溶液生长聚乙烯单晶的影响,表明γ-射线辐照在单晶的规则折叠区也引起了不可忽视的结构缺陷或畸变。     

Dehydration Kinetics of Lithium Sulfate Monohydrate Single Crystals

Some peculiar properties of lithium sulfate monohydrate dehydration kinetics are investigated. Experiments were carried out under both isothermal and non-isothermal conditions on the bulk single crystals (1 cm). Under both heating modes some new data were obtained. Uncommon high dehydration process rate under isothermal conditions and linear dependence of this rate under non-isothermal ones were discovered. Experiments over the water saturated porous ceramics drying and over the water vapors transmitting through the layer of preliminary dehydrated lithium sulfate were carried out. It is attempted to explain observed phenomena considering heat- and mass-transfer conditions.This revised version was published online in November 2005 with corrections to the Cover Date.