表面张力测定激光快速测量.doc

液体表面张力测定-激光快速测量法 (材料加工-铸造一班 姓名：訾凌君 学号：11S009103) 摘要： 基于插板法测液体表面张力系数的基本原理，介绍了一种利用半导体激光器及准直光学系统输出的矩形平行光束，结合线阵CCD传感器，实现液体表面张力系数快速测量的方法。通过测量激光束两边沿在液体表面的入射角来求得表面张力系数，解决了插板法测液体表面张力系数的液面上升高度和接触角检测难题，避免了人为因素的影响。推导了矩形激光束两边沿在液体弯月面的入射角与表面张力系数的关系， 以及CCD用测量激光入射角的计算公式，并进行了参数设计和误差分析。结果表明：为了提高液体表面张力系数的测量精度，在满足测量条件下应采用尽可能大的矩形激光束宽度、激光入射角和CCD相对距离。理论分析表明，当光束宽度的测量误差为５μｍ时，水的表面张力系数测量精度为１％。若将光束宽度的测量误差减小到2μｍ，则水的表面张力系数理论精度可达0.5%。实验结果证明了水的表面张力系数测量精度达到１％。 关键词：插板法，表面张力，激光快速测量，CCD； Abstract：A new quick measuring method for liquid surface tension by a parallel rectangle beam of diode laser and two pieces of linear array CCD sensors is presented. To avoid individual influence, liquid surface tension is measured by detecting angles of incidence at cylindrical liquid menisci instead of detecting climb height of liquid on flashboard. The relation between surface tension and the angle of incidence and calculation formulas for the incidence angle measured with CCDS are developed based on the fundamentals of plate insertion method. The parameters are designed, and their errors are analyzed, the analysis shows that by a wider laser beam and big incidence angles, as well as keeping a long distance between two CCD sensors ,the accuracy of laser beam is an important factor to accuracy of liquid surface tension measurement. For example ,to measure water surface tension with a laser beam with of 1mm and errors of 5ｕm ,the surface tension measurement accuracy is 1%,if reduce the beam with errors to 2ｕm ,the surface tension measurement accuracy will be 0.5%. Experimental results have proved that the surface tension of water measurement accuracy is better than 1% with this method. Keywords: plate insertion method, surface tension, quick measuring with laser, CCD; 1、前言 液体表面张力测量在化学、医药、生物工程等领域具有重要意义，根据液体表面张力的大小可以确定表面活性并计算表面活性剂在溶液表面的吸附量［1-2］；在合金液体体系中，借助于表面张力还可以评价金相组织及孕育效果等重要参数［3-5］。 插板法（Neumann测量法） 是一种较简便的测量液体表面张力系数的方法。但由于界面有时并非很清晰，要准确测量液体在插板外表面的上升高度及接触角较困难,所以利用插板法测量表面张力时， 通常采用照像放大技术。先测出液体在固体表面上升的实际高度h， 然后通过在最高