PET/PC共混体系结晶行为研究进展

聚对苯二甲酸乙二醇酯(PET)／聚碳酸酯(PC)合金材料是综合性能优异的工程塑料,对其结晶行为的研究,可为设计,调节及控制材料的性能提供理论基础。评述了近年来PET／PC共混体系结晶行为研究的最新工作和理论进展,包括PET／PC共混体系酯交换、相容性及结晶性的关系,退火对PET／PC共混体系结晶行为的影响,第三组分对PET／PC共混体系结晶行为的影响,PET／PC共混体系结晶动力学以及PET／PC共混体系高压结晶行为的研究。并对今后的深入研究作了展望。     

Eu掺杂SiC_xO_y薄膜的Eu~(3+)发光机制

利用磁控溅射技术在低温250℃下制备Eu掺杂SiC_xO_y薄膜,研究薄膜的Eu~(3+) 发光激发机制。实验结果表明,薄膜的发光谱由来自基体材料的蓝光和来自Eu~(3+) 的红光组成;随着薄膜中Eu含量由0.19%增加到2.27%,其红光强度增加3倍左右,而蓝光逐渐减弱。Raman光谱及荧光瞬态谱分析表明,其蓝光由中立氧空位缺陷发光中心引起。结合薄膜的Eu~(3+) 激发光谱分析,SiC_xO_y∶Eu薄膜的红光增强源于薄膜中Eu~(3+) 离子浓度的增加和/或基体材料的中立氧空位缺陷发光中心与Eu~(3+) 离子的能量转移。     

Growth characteristics of amorphous-layer-free nanocrystalline silicon films fabricated by very high frequency PECVD at 250 ℃

Amorphous-layer-free nanocrystalline silicon films were prepared by a very high frequency plasma enhanced chemical vapor deposition(PECVD) technique using hydrogen-diluted SiH4 at 250 C.The dependence of the crystallinity of the film on the hydrogen dilution ratio and the film thickness was investigated.Raman spectra show that the thickness of the initial amorphous incubation layer on silicon oxide gradually decreases with increasing hydrogen dilution ratio.High-resolution transmission electron microscopy reveals that the initial amorphous incubation layer can be completely eliminated at a hydrogen dilution ratio of 98%,which is lower than that needed for the growth of amorphous-layer-free nanocrystalline silicon using an excitation frequency of 13.56 MHz.More studies on the microstructure evolution of the initial amorphous incubation layer with hydrogen dilution ratios were performed using Fourier-transform infrared spectroscopy.It is suggested that the high hydrogen dilution,as well as the higher plasma excitation frequency,plays an important role in the formation of amorphous-layer-free nanocrystalline silicon films.     

多组分聚合物体系热力学理论研究进展

概述了多组分聚合物体系热力学理论研究中,从经典的Flory-Huggins平均场理论到Prigogine-Flory现代状态方程理论(EOS)的发展历程,着重讨论了用Flory的EOS及其简化理论研究各种类型聚合物共混体系相容性的发展状况.     

具浓度相关迁移率和梯度相关位势的3维Cahn-Hilliard方程

In this paper we investigate the initial boundary value problem of Cahn-Hilliard equation with concentration dependent mobility and gradient dependent potential.By the energy method and the theory of Campanato spaces,we prove the existence and the uniqueness of classical solutions in 3-dimensional space.     

基于非线性状态空间辨识的气动弹性模型降阶

高维、非线性气动弹性系统的模型降阶是当前气动弹性力学与控制领域的研究热点之一.然而国内外现有的非线性模型降阶方法仍存在辨识算法复杂、精度有待提高等问题.本研究提出了一种基于非线性状态空间辨识的跨音速气动弹性模型降阶方法.首先,该方法基于非定常空气动力的单位脉冲响应数据,采用特征系统实现算法对非线性状态空间模型的线性动力学部分进行系统辨识.其次,引入状态和控制输入的非线性函数,采用优化算法对非线性函数的系数矩阵进行优化,进而得到考虑非线性效应的空气动力降阶模型.为了验证该降阶模型在预测跨音速气动弹性力学行为的精确性,本文以三维机翼为研究对象,分别从基于非线性降阶模型的气动力辨识、跨声速颤振边界计算和极限环振荡预测三方面进行了算例验证,并与现有的模型降阶方法进行了对比,进一步说明本文所提出方法的有效性.研究结果表明,该降阶模型对上述三类问题的计算精度与直接流-固耦合方法相吻合,可用于高效预测飞行器跨声速气动弹性力学行为.     

二烯丙基双酚A醚接枝聚乙烯增容聚碳酸酯/聚乙烯合金中的纤维化增韧现象

采用二烯丙基双酚A醚 (DBAE)接枝聚乙烯 (DBAE g PE)作为聚碳酸酯 (PC) /聚乙烯 (PE)合金的增容剂 ,通过测试合金的冲击强度和裂纹扩展功 (G1C)发现 ,PC含量约为 15份时 ,被增容的合金出现超常的增韧现象 .对合金的断裂表面形态用扫描电子显微镜 (SEM )观察发现 ,未增容的合金呈典型的脆性断裂 ,增容的合金在PC为 15份时 ,PC出现明显的塑性变形 ,形成纤维 .本文就此提出纤维化增韧机制 ,并结合结构模型用纤维化增韧机制初步解释了PC/PE合金的超常增韧现象 .     

聚合物在高压下的结构、形态和性能（下）

聚合物在高压下的结构、形态和性能（下）张雄伟，黄锐（成都科技大学塑料工程系，成都，６１００６５）在上篇中我们介绍了结晶性聚合物在高压下结晶的结构和形态。本篇将介绍聚合物在高压下的结晶动力学和热力学以及聚合物在高压下的退火等方面内容。２高压结晶动力学研...     

Complexity of asymptotic behavior of solutions for the porous medium equation with absorption

In this paper we analyze the large time behavior of nonnegative solutions of the Cauchy problem of the porous medium equation with absorption u t-u m + γup = 0, where γ≥ 0, m 1 and p m + 2/N . We will show that if γ = 0 and 0 μ 2N/(N(m-1)+2), or γ 0 and 1/(p-1)μ2N/(N(m-1)+2), then for any nonnegative function φ in a nonnegative countable subset F of the Schwartz space S (R N ), there exists an initial-value u0 ∈C(RN) with lim x →∞ u 0 (x) = 0 such that φ is an ω-limit point of the rescaled solutions t μ/2 u(t β·, t), where β =[2-μ(m-1)]/4 .