Ge H, Suszynski W J, Davis H T, Scriven L E
Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, MN, USA.
J Microsc. 2008 Jan;229(Pt 1):115-26. doi: 10.1111/j.1365-2818.2007.01872.x.
A new controlled environment vitrification system (CEVS) has been designed and constructed to facilitate examination by cryogenic scanning electron microscopy (Cryo-SEM) of initial suspension state and of microstructure development in latex, latex-composite and other coatings while they still contain solvent. The new system has a main chamber with provisions for coating as well as drying, and for well-controlled plunging into cryogen. An added subsidiary chamber holds samples for drying or annealing over minutes to days before they are returned to the main chamber and plunged from it. In the main chamber, samples are blade-coated on 5 x 7 mm pieces of silicon wafer and held at selected temperature and humidity for successively longer times, either there or after transfer along a rail into the subsidiary chamber. They are then placed in the sample holder mounted on the plunge rod, so as to permit adjustment of the sample's attitude when it plunges, at controlled speed, into liquid ethane at its freezing point, to a chosen depth, in order to solidify the sample without significant shear or freezing artifacts. The entries of plunging samples and related sample holders into liquid ethane were recorded with a high-speed, high-resolution Photron digital camera. The data were interpreted with a new hypothesis about the width of the band of extremely rapid cooling by deeply subcooled nucleate boiling below the line of entry. Complementary cryo-SEM images revealed that the freezing rate and surface shearing of a sample need to be balanced by adjusting the plunging attitude.
一种新的可控环境玻璃化系统（CEVS）已被设计和构建，以便在乳胶、乳胶复合材料及其他涂层仍含有溶剂时，通过低温扫描电子显微镜（Cryo-SEM）对其初始悬浮状态和微观结构发展进行检查。新系统有一个主腔室，具备涂层、干燥以及精确控制投入低温介质的功能。一个附加的辅助腔室用于存放样品，可在数分钟至数天内进行干燥或退火，之后再送回主腔室并从主腔室投入低温介质。在主腔室中，将样品用刀片涂覆在5×7毫米的硅片上，并在选定的温度和湿度下保持连续更长时间，可在主腔室内进行，也可沿着轨道转移至辅助腔室后进行。然后将它们放置在安装在 plunging 杆上的样品架中，以便在样品以可控速度投入其冰点的液态乙烷至选定深度时，能够调整样品的姿态，从而在不产生显著剪切或冻结伪像的情况下使样品固化。用高速、高分辨率的 Photron 数码相机记录投入样品及相关样品架进入液态乙烷的过程。利用关于在入口线以下深度过冷的核态沸腾引起的极快速冷却带宽度的新假设对数据进行了解释。互补的低温扫描电子显微镜图像显示，需要通过调整投入姿态来平衡样品的冷冻速率和表面剪切力。
