聚偏二氟乙烯/(Y0.97Eu0.03)2O3稀土氧化物纳米复合材料制备、形貌及发光性能

借助超声技术采用一种简便易行的共沉淀方法制备出聚偏二氟乙烯(PVDF) /钇铕稀土氧化物((Y0.97Eu0.03)2O3)纳米粒子发光纳米复合材料。复合材料的断面形貌和(Y0.97Eu0.03)2O3纳米粒子在PVDF基体中的分散状态通过扫描电子显微镜(SEM)进行了研究,其发光性质通过荧光光谱进行表征。SEM结果表明:当(Y0.97Eu0.03)2O3纳米粒子添加量在1% ～5%时,(Y0.97Eu0.03)2O3纳米粒子在PVDF基体中形成尺寸在50 nm～2μm的团聚体,其尺寸随(Y0.97Eu0.03)2O3添加量增加而增大;当(Y0.97Eu0.03)2O3添加量小于1%时, (Y0.97Eu0.03)2O3纳米粒子在PVDF基体中实现了较好分散。发光光谱结果表明制备的纳米复合材料具有明显的红光发射特征,对应于(Y0.97Eu0.03)2O3纳米粒子的本征发射。制备的高分子发光纳米复合材料将来有望在光学材料中获得应用。     

Local vibration assisted molecular configurations in poly(vinylidene fluoride) of ordered ferroelectric phase in N,N-dimethylformamide

Amide-based polymer liquids are important for developing biological and optical colloids or nanofluids. Functionalized properties arise from specific molecular structures. In this investigation, we report model molecular configurations of a polymer liquid, 0.3 g/L poly(vinylidene fluoride) (PVF₂) dissolved in liquid N,N-dimethylformamide (DMF), based on the characteristic IR vibration bands. Peculiarly, a ferroelectric β-PVF₂ phase reorders on a linear configuration in support with the DMF molecules, showing a characteristic band 840 cm^− 1 (CH₂ rocking and CF₂ asymmetric stretching) with the trans band at 1275 cm^− 1. Four CO stretching bands ν₁⁰, ν₁¹, ν₁², and ν₁³ of 1650, 1675, 1725, and 1760 cm^− 1 (bandwidth Δν_½ = 180 cm^− 1 in the four bands) arise in four major configurations of DMF-PVF₂ pairs (or derivatives). Only one prominent ν₁⁰ band 1660 cm^− 1 (Δν_½ = 75 cm^− 1) incurs with a shoulder ν₁¹ of 1725 cm^− 1 (Δν_½ = 25 cm^− 1) in two DMF configurations. A ferroelectric field cased in presence of β-PVF₂ leads to enhance IR absorption by as much as an order of magnitude. It leads to converging non-bonding electron density on the amide moiety.     

聚(偏氟乙烯-三氟乙烯)纳米薄膜极化反转与疲劳特性

采用旋涂法制备了厚度为140 nm的聚(偏氟乙烯-三氟乙烯)[P(VDF-TrFE)]纳米薄膜, 研究了不同退火温度以及环境相对湿度对薄膜的极化反转和疲劳性能的影响. 运用X射线衍射仪、扫描电子显微镜和傅里叶变换红外光谱仪等测试技术对薄膜的微结构进行了表征. 实验结果表明, 通过不同温度的退火处理, P(VDF-TrFE)铁电薄膜的结晶度随着退火温度的升高而不断提高, 并且一定的温度范围内的退火处理可以提高薄膜的极化性能; 此外, P(VDF-TrFE) 铁电薄膜性能还表现出一定的环境湿度的敏感特性, 这与薄膜的物理性能和结构特点密切相关; P(VDF-TrFE)铁电薄膜在不同的环境湿度条件下 表现出较好的电学特性, 其漏电流均保持在10 ^-7A/cm² 的较低水平. 本工作揭示了再退火过程对薄膜的极化反转速度和疲劳恢复特性的影响, 并结合薄膜二次疲劳结果, 探讨了薄膜可逆的内部疲劳恢复特性机理.     

Crystallizaion and surface morphology of poly(vinylidene fluoride)/poly(methylmethacrylate) films by solution casting on different substrates

The dependence of surface structure of the poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) films by solution casting on properties of seven substrates was investigated by wide angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). It was revealed that the polyblend films obtained by casting onto each substrate contained exclusively β phase PVDF. Higher crystallinity of the film was obtained by casting onto ceramic, polytetrafluoroethylene (PTFE), copper (Cu), stainless steel and glass substrates than that by casting onto aluminium (Al) and polypropylene (PP) substrates, depending on the degree of close lattice matching. The surface crystalline structure of PVDF was strongly affected by the wettability of substrate. The largest size of PVDF spherulitic crystal structure with about 6 μm presented in the casting film grown at the air/solution interface on glass substrate, while the smallest spherulite size with about 3 μm was generated by casting onto PTFE, stainless steel and PP substrates. It implied that the higher surface tension the substrate had, the larger PVDF spherulite grew at the air/solution interface.     

Friction and Wear Behavior of Polyamide 66/Poly(vinylidene fluoride) Blends

The tribological performance of PA66 and PVDF blends was investigated by a block‐on ring sliding friction and wear tester. The appropriate amount of PVDF can decrease the friction coefficient and improve the wear resistance of PA66. Moreover, the appropriate amount of PA66 can improve the wear resistance of PVDF. SEM analysis shows that PVDF is noncompatible with PA66, and the blend presents a two‐phase structure. A smooth worn surface is a main reason for improving the frictional and wear properties of the PA66/PVDF blend. Besides, slight debris is an important factor in improving the wear resistance of the PA66/PVDF blend. FT‐IR analysis shows that the oxidation and degradation behavior of PVDF is effectively controlled in the PA66/PVDF blends. Therefore, the blend of PA66 and PVDF is a potential polymer material for tribological applications.     

Radiation effects on poly(vinylidene fluoride)

Melt-crystallized poly(vinylidene fluoride)s (PVF₂) with different crystallization histories were irradiated with γ-rays within the range of irradiation doses 0–83 Mrad. The effects on the crystalline structure and mechanical properties have been measured, compared, and discussed. The degree of crystallinity of the samples was found to increase with radiation dose. The differential scanning calorimeter scans of the quenched samples indicate that there are two melting peaks, and that the area of the lower temperature peak increases while the area of higher temperature peak decreases with increasing dose. Yield stress and breaking stress for all samples are not significantly affected by irradiation but elongation at break is.     

Effect of PMMA on crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate) blend prepared in semi-dilute solutions

Films of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend were derived from a special procedure of casting semi-dilute solutions. Hydrophilic character and crystallization of PVDF were optimized by variation of PMMA concentration in PVDF/PMMA blends. It was found that a PVDF/PMMA blend containing 70 wt% PMMA has a good performance for the potential application of hydrophilic membranes via thermally induced phase separation. The films presented β crystalline phase regardless of PMMA content existed in the blends. Thermal analysis of the blends showed a promotion of crystallization of PVDF with small addition of PMMA which induced larger lamellar thickness of PVDF, leading to the largest spherulitic crystal of PVDF (10 wt% PMMA) is about 8 μm. SEM micrographs illustrated no phase separation occurred in blends, due to the high compatibility between PVDF and PMMA.     

Studies on poly(vinylidene fluoride-co-hexafluoropropylene) based gel electrolyte nanocomposite for sodium-sulfur batteries

Experimental investigations on a sodium ion conducting gel polymer electrolyte nanocomposite based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with silica nanoparticles are reported. The gel nanocomposites have been obtained in the form of dimensionally stable, transparent and free-standing thick films. Physical characterization by X-ray diffraction (XRD), Fourier transform Infra-red (FTIR) spectroscopy and Scanning electron microscopy (SEM) have been performed to study the structural changes and the ion-filler-polymer interactions due to the dispersion of SiO₂ nanoparticles in gel electrolytes. The highest ionic conductivity of the electrolyte has been observed to be 4.1 × 10⁻³ S cm^− 1 at room temperature with ~ 3 wt.% of SiO₂ particles. The temperature dependence of the ionic conductivity has been found to be consistent with Vogel-Tammen-Fulcher (VTF) relationship in the temperature range from 40 to 70 °C. The sodium ion conduction in the gel electrolyte film is confirmed from the cyclic voltammetry, impedance analysis and transport number measurements. The value of sodium ion transport number (t_Na+) of the gel electrolyte is significantly enhanced to a maximum value of 0.52 on the 15 wt.% SiO₂ dispersion. The physical and electrochemical analyses indicate the suitability of the gel electrolyte films in the sodium batteries. A prototype sodium-sulfur battery, fabricated using optimized gel electrolyte, offers the first discharge capacity of ~165 mAh g^− 1 of sulfur.     

Investigation on crystalline structure and dielectric relaxation behaviors of hot pressed poly(vinylidene fluoride) film

The dielectric relaxation behaviors of hot pressed poly(vinylidene fluoride) (PVDF) film have been studied using dielectric spectroscopy in the frequency domain from 20 Hz to 5 MHz at temperatures between 20 °C and 200 °C. Crystalline/amorphous interphase is suggested with methods of FTIR, XRD, and DSC. Frequency and temperature dependence of dielectric spectroscopy reveals the relaxation behavior and structural dynamics of the samples, and three types of relaxation processes are suggested, α_Ac relaxation process contributed by the hopping transport process near the periphery of conduction band or valence zones at Fermi energy, α_c relaxation process related to the structure change of crystal lattice trapped dipoles in crystalline regions, and α_a relaxation process arising from segmental dipole rearrangement of interphases in amorphous regions. Cole-Cole and Havriliak-Negami experimental equations were utilized to analyze these relaxation processes, and differences of Arrhenius parameters for α_Ac and α_c relaxation processes obtained from Cole-Cole and Havriliak-Negami equations were discussed in detail. Activity energy of different relaxation processes obtained from Arrhenius equation and VFT equation indicates non-single thermal activation mechanism for hot pressed PVDF film.     

Dielectric Loss Suppression of Silver/Poly(vinylidene fluoride) Composite Films with Polydopamine

The preparation and dielectric properties of silver-polydopamine/poly(vinylidene fluoride) (Ag-PDOP/PVDF) composite films with suppressed dielectric loss are reported. The dielectric loss tangents of the composite films were found to be rather low similar to that of pure PVDF over the frequency range 100 Hz to 30 kHz, almost regardless of the Ag content, and even lower than that of pristine PVDF in the relatively high frequency region. The nanoscale structure comprised of Ag nanoparticles (Ag NPs), isolated by the PDOP coating and the PVDF matrix, hindered the formation of percolative networks, resulting in the decreased conduction loss in the composite films, even at a high filler loading. The strong interfacial interaction between the Ag@PDOP particles and the PVDF matrix also contributed to the restrained interfacial loss. Consequently, these composite films had higher permittivity and smaller dielectric loss than the PVDF matrix at relatively high frequencies, and would thus be attractive for physically small capacitor applications in electronics and electric power systems.     

Poly(vinylidene fluoride) Crystallization Behavior and Membrane Structure Formation Via Thermally Induced Phase Separation with Benzophenone Diluent

Microporous poly(vinylidene fluoride) (PVDF) membranes were prepared by thermally induced phase separation (TIPS) at different quenching temperatures with benzophenone as the diluent. The crystallization behavior and crystal structure of PVDF in PVDF/benzophenone systems were investigated by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). The different PVDF concentrations had a remarkable effect on PVDF crystallization behavior and resulted in different membrane structures. Spherulitic structures were vague when the PVDF/benzophenone solution was quenched to ?8°C; however, discernable spherulitic structures were obtained when quenched to 34 and 49°C. Additionally, two phase separation mechanisms (solid–solid (S–S) and solid–liquid (S–L) phase separation) were observed during membrane preparation. It was revealed by scanning electron microscopy (SEM) that microporous membranes had more discernable spherulitic structures formed by S–L phase separation than by S–S phase separation, which induced macrovoids and irregular pores on the fracture surfaces of membranes.     

三螺旋DNA分子poly(dT)·poly(dA)·poly(dT)的构型和振动谱

我们计算了ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）的Ｈｏｗａｒｄ模型的原子笛卡尔坐标，并利用晶格动力学方法对模型进行了简正分析。结果发现其０ Ｐ ０对称振动模式位于８０４ｃｍ－１，这和８１０ｃｍ－１附近没有拉曼和红外谱线的实验结果不符。在８００～１０００ｃｍ－１的范围内只有四个振动模式，明显少于拉曼和红外光谱在该范围内的谱线数目。所以我们认为Ｈｏｗａｒｄ模型需要进一步地完善和修正，ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）必须具有三条不完全一致的脊骨     

Electromechanical actuation of CNT/PVDF composite films based on a bridge configuration

Bridged strips consisting of carbon nanotubes and poly(vinylidene fluoride) are developed, which exhibit notable deflection in response to very low driven voltages( 1 V), because of both the excellent conductivity of the unique carbon nanotube film and the powerful thermal expansion capability of the polymer. The actuators demonstrate periodic vibrations motivated by the alternating signals. The amplitude of displacement is dependent not only on the driven voltage but also on the applied frequency. The mechanism of actuation is confirmed to be the thermal power induced by the electrical heating. By accelerating the dissipation of heat, the vibration response at higher frequencies can be significantly enhanced.The useful locomotion shows great promise in potential applications such as miniature smart devices and micro power generators.     

Antibacterial activities of surface modified electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibrous membranes

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane, with its excellent chemical and mechanical properties, has good potential for broad applications. However, due to its hydrophobic nature, microbial colonization is commonly encountered. In this work, electrospun PVDF-HFP fibrous membranes were surface modified by poly(4-vinyl-N-alkylpyridinium bromide) to achieve antibacterial activities. The membranes were first subjected to plasma pretreatment followed by UV-induced surface graft copolymerization of 4-vinylpyridine (4VP) and quaternization of the grafted pyridine groups with hexylbromide. The chemical composition of the surface modified PVDF-HFP electrospun membranes was studied by X-ray photoelectron spectroscopy (XPS). The morphology and mechanical properties of pristine and surface modified PVDF-HFP fibrous membranes were characterized by scanning electron microscopy (SEM) and tensile test, respectively. The antibacterial activities of the modified electrospun PVDF-HFP fibrous membranes were assessed against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The results showed that the PVDF-HFP fibrous membranes modified with quaternized pyridinium groups are highly effective against both bacteria with killing efficiency as high as 99.9999%.     

分段表面放电光抽运XeF(C-A)激光器

阐述了分段表面放电光抽运XeF(C -A)激光器的设计和实验技术。分段表面放电辐射源在 140nm～ 170nm辐射区域亮度温度Tb≈ 15× 10 3K ,用该辐射源作抽运源离解XeF2 获得了XeF(C -A)蓝绿 (4 70nm～ 495nm)激光输出 ,激光脉宽为 340ns、光谱宽度为 15nm。     

Resonant-type Smooth Impact Drive Mechanism (SIDM) actuator using a bolt-clamped Langevin transducer

The Smooth Impact Drive Mechanism (SIDM) is a linear piezoelectric actuator that has seen practically applied to camera lens modules. Although previous SIDM actuators are easily miniaturized and enable accurate positioning, these actuators cannot actuate at high speed and cannot provide powerful driving because they are driven at an off-resonant frequency using a soft-type PZT. In the present study, we propose a resonant-type SIDM using a bolt-clamped Langevin transducer (BLT) with a hard-type PZT. The resonant-type SIDM overcomes the above-mentioned problems and high-power operation becomes possible with a very simple structure. As a result, we confirmed the operation of resonant-type SIDM by designing a bolt-clamped Langevin transducer. The properties of no-load maximum speed was 0.28 m/s at driving voltages of 80 V_p-p for 44.9 kHz and 48 V_p-p for 22.45 kHz with a pre-load of 3.1 N     

光泵浦双反射带半导体激光器的热效应有限元分析

给出了808 nm/980 nm双反射带布拉格反射镜的反射谱线,建立了光泵浦双反射带半导体激光器件的热学模型及其内部热载荷分布形式,运用有限元分析方法,详细分析了双反射带光泵浦半导体激光器件的热学特性。结果表明,对于激射光反射率为99.96%的单反射带和双反射带布拉格反射镜结构的垂直外腔面发射半导体激光器件,前者的散热性能较好,而后者的最大温升明显低于前者。本文的分析结果可为半导体激光器件的结构优化和实验研究提供理论参考。     

Synthesis of the poly(N-isopropylacrylamides) containing tetraarylporphyrin substituents

In a brief form, the authors provide their developed methods of synthesis and modification of the poly(N-isopropylacrylamide) derivatives containing meso-tetraarylporphyrin substituents in the side chain. The specific features of absorption spectra of the compounds obtained and their dependence on the method of introduction of porphyrin groups into the polymer are discussed. The physical and chemical characteristics of the polymers described are given. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 538–541, July–August, 1999.     

Preparation of conductive nanocomposites based on poly (aniline-co- butyl 3-aminobenzoate) and poly (aniline-co-ethyl 3-aminobenzoate) by solution blending method

The polyaniline (PANI) is a widely studied conducting polymer due to its application in several devices such as biosensor, gas sensor etc. Known methods to produce PANI composites may be essentially reduced to two distinct groups: synthetic methods based on aniline polymerization in the presence of or inside a matrix polymer, and blending methods to mix a previously prepared PANI with a matrix polymer. Poly (aniline-co-butyl 3-aminobenzoate) (ANI-co-BAB) and poly (aniline-co-ethyl 3-aminobenzoate) (ANI-co-EAB) are prepared as conducting copolymers in nanoscale by chemical oxidation method under ultrasonic irradiation. The different molar ratio of aniline to butyl 3-aminobenzoate and ethyl 3-aminobenzoate are used in the preparation of copolymers. Conductive nanocomposites based on ANI-co-BAB or ANI-co-EAB with poly (styrene-alt-maleic acid) (PSMAC), and polystyrene are prepared by solution blending method. The obtained conductive composites formed films with good homogeneity and flexibility. The conductivity of the obtained nanocomposites is measured with a four-probe method. The electrical conductivity of the composites (ANI-co-EAB)/PSMAC/PS and (ANI-co-BAB)/PSMAC/PS are 24?×?10^?5?S?cm^?1 and 31?×?10^?5?S?cm, respectively. Our results show that the (ANI-co-BAB)/PSMAC/PS composite has more conductivity than (ANI-co-EAB)/PSMAC/PS composite. The copolymers and composites in nanoscale are characterized by FT-IR and ¹H NMR spectral data. The surface morphology was studied using SEM analysis. Also, their grain size is measured using XRD studies.     

Cardinalities of poly(p-phenylene) graphs

Recurrence relation for the cardinalities of linear and cylindrical poly(p-phenylene) (PPP) compounds has been developed that requires the cardinalities of two of their immediate lower homologues. Such recurrence relation reduces into analytical expressions for the cardinalities under transfer matrix formalism. Ambient condition density and bulk modulus of linear PPPs are found to bear excellent linear correlation with the inverse of logarithm of their cardinalities. Topological bond orders obtained from the cardinalities of such PPPs have been found to have good linear correlations with the respective Hückel bond orders.