Morphological stability analysis of vesicles with mechanical-electrical coupling effects

Using a recently established liquid crystal model for vesicles, we present a theoretical method to analyze the morphological stability of liquid crystal vesicles in an electric field. The coupled mechanical-electrical effects associated with elastic bending, osmotic pressure, surface tension, Max- well pressure, as well as flexoelectric and dielectric proper- ties of the membrane are taken into account. The first and second variations of the free energy are derived in a com- pact form by virtue of the surface variational principle. The former leads to the shape equation of a vesicle embedded in an electric field, and the latter allows us to examine the stabil- ity of a given vesicle morphology. As an illustrative exam- ple, we analyze the stability of a spherical vesicle under a uniform electric field. This study is helpful for understanding and revealing the morphological evolution mechanisms of vesicles in electric fields and some associated phenomena of cells.

纳米SiO_2表面处理对质子交换膜热稳定性的影响

研究了纳米SiO2在偶联剂修饰后对质子交换膜的热稳定性及热降解动力学的影响。利用热重分析（TG—DTG）在氯气气氛中，升温速率分别为5℃、10℃和20℃的条件下，采用Kissinger、Flynn-Wall—Ozawa、Friedman和Modified Coats—Redfem方法对膜SiO2改性后的非等温动力学数据进行了分析。TG-DTG曲线显示SiO2改性后质子交换膜分解率达到10％和15％时，最低热降解温度分别为392．4℃和429．5℃，比改性前分别提高26．8℃和57．7℃。改性后质子交换膜为一步法分解，分解的温度区间为405℃～550℃，热分解的表观活化能E和指前因子lnA分别为223．110／mol和31．63min-1，分解过程属于一维扩散（D1）机理控制。

磷钨酸表面处理对燃料电池质子交换膜热稳定性的影响

研究了磷钨酸掺杂改性后质子交换膜的热稳定性及热降解动力学,利用热重分析在氮气气氛下和升温速率分别为5℃、20℃和30℃时,采用Kissinger、Flynn-Wall-Ozawa、Friedman和Starink方法对磷钨酸改性后的非等温动力学数据进行了分析。热失重曲线显示磷钨酸改性后质子交换膜分解率达到5%和10%时,最低热降解温度分别为173.6℃和284.8℃。采用不同方法的计算结果显示,改性后膜分解反应受D2机理控制,表观活化能约为163.74 kJ/mol。改性前后膜的电导率(σ)分别为8.34×10-7S/cm及2.57×10-5S/cm。