变温下油脂自由体积和晶型结构演化的正电子湮没寿命研究  

Study of Free Volume and Phase Transitions in Triacylglycerol Crystals Using Temperature-dependent Positron Annihilation Lifetime Spectroscopy

作　　者：段会 张鹏[2] 刘福雁 于啸天 况鹏[2] 张玉包[2] 张仁刚[1] 于润升[2] 曹兴忠[2,3] 王宝义 DUAN Hui;ZHANG Peng;LIU Fu-yan;YU Xiao-tian;KUANG Peng;ZHANG Yu-bao;ZHANG Ren-gang;YU Run-sheng;CAO Xing-zhong;WANG Bao-yi(College of Science,Wuhan University of Science and Technology,Wuhan 430081,China;Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;University of Chinese Academy of Sciences,Beijing 100039,China)

机构地区：[1]武汉科技大学理学院,湖北武汉430081 [2]中国科学院高能物理研究所,北京100049 [3]中国科学院大学,北京100039

出　　处：《分析测试学报》2024年第10期1651-1657,共7页Journal of Instrumental Analysis

基　　金：国家重点研发计划(2019YFA0210002);国家自然科学基金(12105305,11975173,12175261,12275299);中国科学院高技术产业化项目(2023000188)。

摘　　要：甘油三酯具有独特的同质多晶现象,其结晶和熔化特性对油脂产品性能及工业应用至关重要。利用正电子湮没寿命谱(PALS)可在原子尺度对结晶态甘油三酯的微观结构变化进行特征化描述。当正电子进入分子材料时,会与周围的电子形成电子偶素(电子-正电子的束缚态),其寿命反映了材料中空洞(自由体积)的大小。该文使用PALS首次研究了5种饱和脂肪酸甘油三酯的多晶性和晶型转变过程,包括甘油三月桂酸酯、甘油三肉豆蔻酸酯、三棕榈酸甘油酯、三硬脂酸甘油酯、花生酸甘油三酯。正电子数据和由其他表征手段得到的晶型变化规律很好符合。用正电子观察到更长分子链甘油三酯固相收缩成更稳定的晶型时有空洞形成,以及α晶在固-固转化过程中形成了2种β晶形态。Polymorphism is a specific feature of the triacylglycerols.The crystallization and melting properties are essential for the characteristics and industrial applications of fats.Positron annihilation lifetime spectroscopy(PALS)allows for the characterization of microstructural changes in triacylglyc⁃erol crystals at the atomic scale.When positrons enter molecular materials,they form positronium(electron-positron bound states)with surrounding electrons,whose lifetime reflects the size of mo⁃lecular-voids(free volumes).In this paper,PALS was used to study the polymorphism and phase transition processes of five saturated monoacid triacylglycerides for the first time,including trilaurin,trimyristin,tripalmitin,tristearin and arachidin.The patterns of crystal phase transitions obtained from the PALS are in good agreement with those from other characterization methods.The positrons experiments revealed the formation of voids during the solid phase contraction of longer-chain triglyc⁃erides into more stable crystal forms,as well as the transformation from theαform into twoβforms by solid-solid transformations.

关 键 词：甘油三酯 正电子湮没寿命谱 同质多晶 电子偶素 

分 类 号：O469[理学—凝聚态物理]