CaCu3Ti4O12 陶瓷介电模量响应特性的研究

由于CaCu₃Ti₄O₁₂巨介电常数陶瓷的低频区直流电导较大, 本文采用模量 M"-f频谱表征与分析了低频和高频的两个松弛极化过程. 研究认为, 这两个特征峰属于晶界区Schottky 势垒耗尽层边缘深陷阱的电子松弛过程, 其中高频松弛峰起源于晶粒本征缺陷的电子松弛过程, 而低频松弛峰则为与氧空位有关的松弛极化过程. 对于CaCu₃Ti₄O₁₂这类低频下具有高直流电导的陶瓷材料, 采用模量频谱能更有效地分析研究其损耗极化机理. 关键词： 3Ti₄O₁₂陶瓷')" href="#">CaCu₃Ti₄O₁₂陶瓷 模量 松弛过程 电导     

聚对苯乙炔MOPPV/ZnSe量子点复合材料太阳电池性能研究

基于量子点材料的特殊物理性能和量子点聚合物复合材料高的光电转换性能, 本文在MOPPV溶液中制备了粒度可控、 结晶性好、颗粒尺寸约为3.75 nm的ZnSe量子点材料, 最终获得不同质量比的MOPPV/ZnSe复合材料. 分别使用X射线衍射、透射电子显微镜、紫外可见吸收光谱等研究其特性结果表明MOPPV与ZnSe量子点可以有效地复合且发生光诱导电荷转移; 通过对MOPPV、ZnSe和MOPPV/ZnSe复合材料太阳电池性能的研究发现, 与MOPPV和ZnSe单体相比复合材料光伏特性呈现增加的趋势, 并且复合材料光电性能随着ZnSe量子点材料质量浓度的增加呈现先增大后减小的现象, 当MOPPV和ZnSe的质量比为1:1时, 其转换效率最大, 开路电压为0.516 V, 短路电流为2.018 mA, 填充因子为25.53%, 转换效率为0.167%. 关键词： 量子点 复合材料 伏安特性     

Stress-induced textures in polymers

The effect of an applied stress on the annealing texture of polyethylene is demonstrated by means of stress annealing experiments. Cold-drawn polyethylene specimens were annealed for various times at 126°C with and without a compression stress of 0.4 kg/mm² normal to the drawing direction. The observed change in the annealing texture resulting from the compression stress indicates that stress-induced alignment of the crystalline regions in the polyethylene occurs (stress-induced texture). The alignment may be understood in terms of the elastic energy stored in the material during annealing. The stored elastic energy is minimized by aligning the crystallites such that the crystallographic direction of lowest modulus is parallel to the direction of the applied stress. The importance of this observation for the interpretation of the high-temperature deformation textures of polymers is discussed.     

Swelling Behavior of Guar Gum-g-Poly(Sodium Acrylate -co-Styrene)/Attapulgite Superabsorbent Composites

A series of superabsorbent composites, guar gum-g-poly(sodium acrylate-co- styrene)/attapulgite [GG-g-P(NaA-co-St)/APT], were prepared by simultaneous grafting partially neutralized acrylic acid and hydrophobic styrene (St) onto guar gum in the presence of attapulgite as an inorganic component. Equilibrium swelling capacity strongly depended on the concentration of St, drastically increasing with increasing St concentration to 24.3 mmol/L and then decreasing. The influence of St concentration on the swelling kinetics of the superabsorbent was studied by means of a Schott's second-order model. The proper amount of St is of benefit for the improvement of the initial swelling rate in either distilled water or saline solution. The influence of St concentration on the swelling behaviors in various external media (the aqueous solutions of various salts, pHs, hydrophilic organic solvent/water mixture and surfactants) was also investigated systematically. Results showed that the concentration of St is the key factor influencing equilibrium swelling capacity of the superabsorbent composites in each swelling media, and moderate amounts of St could enhance the responsiveness of the corresponding superabsorbent composite to external stimulation.     

Preparation and Characterization of an Organic/Inorganic Composite Based on Ferrospinel with Poly(Methyl Methacrylate) and Polyaniline

A novel organic/inorganic composite based on LiNi–ferrospinel with poly(methyl methacrylate) (PMMA) and polyaniline (PANI), PANI/PMMA/LiNi_0.5Fe₂O₄ composite, was synthesized via a facile in-situ polymerization process. The structures of the resulting samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy. The optical and thermal properties of the PANI/PMMA/LiNi_0.5Fe₂O₄ composite were studied by fluorescent spectroscopy and thermogravimetry analysis. It was indicated that the existence of LiNi_0.5Fe₂O₄ (LFNO) in the PANI/PMMA/LFNO composite resulted in changes in the fluorescence spectra. The as-obtained composite may have potential for electrical and electromagnetic applications in antistatic materials, electromagnetic shields, radar absorbers, and so forth.     

Role of ion energy flux on the structural and morphological properties of silicon oxy-nitride composite films deposited by plasma focus device

ABSTRACT

Crystalline silicon oxy-nitride (SiON) composite films are deposited on Si substrate for multiple (5, 15, 25 and 50) focus shots (FS) by plasma focus device. The X-rays diffraction patterns reveal the development of various diffraction peaks related to Si, Si₃N₄, and SiO₂ phases which confirms the formation of SiON composite film. The intensity of Si₃N₄ (1 0 2) plane is linearly increased with the increase of FS. The Si₃N₄ (1 0 2) phase does not nucleate for 5 FS. Raman analysis confirms the formation of β–Si–N phase. Raman and Fourier transform infrared spectroscopy analysis reveals that the strength of chemical bonds like Si–N, Si–O formed during the deposition process of SiON composite films is associated with the bonds intensity which in turn depends on the number of FS. The field emission scanning electron microscopic analysis reveals that the surface morphology like size, shape and distribution of micro/nano-dimensional particles, film compactness and the formation of micro-rods, micro-teethes and micro-tubes of SiON composite films is entirely associated with the rise in substrate surface transient temperature which in turn depends on the increasing number of FS. The EDX spectrum confirms the presence of Si (22.5?±?4.7 at. %), N (13.4?±?4.5 at. %) and O (54.7?±?11.3 at. %) in the SiON composite film. The thickness of SiON composite film deposited for 50 FS is found to ～15.47?µm.     

小波变换特征提取的复合材料损伤检测

论述了小波变换及其快速算法，基于小波变换的波形模量极大点来构造全局的相似性度量，并将此应用于复合材料损伤类型的检测     

人造金刚石与硬质合金复合材料的研制

 本实验选用TiH₂及其它微量元素做粘结剂，在DS-029B型六面顶压机上烧结人造金刚石与硬质合金复合材料。实验中，采取TiH₂脱氢与金刚石净化同时进行的工艺，在高真空和一定温度下脱氢，得到高活性的新鲜钛，使其具有更强的粘结作用，以获得高磨耗比的金刚石复合材料。实验中比较了不同净化温度对磨耗比的影响；同一种粘结剂不同含量与磨耗比之间的关系；同时还测试了其耐热性及时间极限。结果表明，这种复合材料在850 ℃下，加热3 min，磨耗比没有明显改变。     

Basic solution of four parallel non-symmetric permeable Mode-III cracks in a piezoelectric/piezomagnetic composite plane

The interaction of four parallel non-symmetric permeable cracks in a piezoelectric/piezomagnetic composite plane subjected to anti-plane shear stress loading was studied by the Schmidt method. The problem was formulated through a Fourier transform into four pairs of dual integral equations, in which unknown variables are jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displacements across the crack surfaces were directly expanded as a series of Jacobi polynomials. Finally, the relationships among the electric displacement, magnetic flux and stress fields near the crack tips were obtained. The results show that the stress, the electric displacement and the magnetic flux intensity factors at the crack tips depend on the lengths and spacing of cracks. It was also revealed that the crack shielding effect is present in piezoelectric/piezomagnetic composites.