上海交通大学 1856 SHANGHAI JIAO TONG UNIVERSITY Chapter 11.Surface and Interface Surface energy surface tension Effect of surface curvature ·Vapor pressure Solubility of small particles Wetting of surfaces ·Gibbs absorption isotherm Review
Chapter 11. Surface and Interface Review
上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Introduction:Surface Surfaces and Interfaces Everything is made of something and has to end somewhere. An atom at a free surface of a solid has greater energy than an atom in the interior of a crystal because it is less tightly bound. Surface energy The sum of all the excess energies of the surface atoms Can be defined in terms of energy,enthalpy, Helmholtz free energy,or Gibbs free energy, depending on the physical constraints placed on (a)由劈开晶体形成的自由键 the definition
Introduction: Surface
上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Introduction:Surface energy Surface energy based on Gibbs free energy dG =-SdT+VdP ydA OF TP A T.P Commonly observed manifestations A liquid droplet tries to minimize its free energy,it assumes a spherical shape Small droplets tend to agglomerate into larger droplets,minimizing their combined surface-to-volume ratios Small particles of metals or ceramics,when pressed into a shape and heated at high temperatures,will“sinter”into a solid mass
Introduction: Surface energy
上游充通大粤 SHANGHALIIAO TONG UNIVERSITY Barerett Media
上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Introduction:Surface energy Image a film of liquid stretched on a frame dx- 21ydx Fdx y=F/21 Y Surface energy with units of dynes per centimeter,or newtons per meter in the SI Soap film system. Y←->f Detail of wire Figure 4.1 Stretching a film-increasing area
Introduction: Surface energy