上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY Surface energy surface tension Y Surface energy with units of dynes per centimeter,or newtons per meter in the SI system. [界面张力] [界面能] SI单位制 N(牛顿)·m1=J(焦耳)m-2 cgs单位制 dyn(达因)·cm-l=erg(尔格)·cm-2
Surface energy / surface tension
上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Surface energy surface tension Surface tension or surface energy Liquid Isotropic Surface energy does not change as the surface is stretched Solids Function of the erystallographic plane that is expected The nature of a solid surface changes as the material is deformed
Surface energy / surface tension
上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Surface energy of materials 口△◇0固体 ▣液/液 3 ■▲◆●液体 Al2O3/LFe Fe 。固/液 ⊙ 品界 ⊙ Mgo SiOz/LFe 金属 、 纯金属的 Fe Hg t-w.r/o 随机晶界 Cu 0.3 0.3 类金属 SiOz 无机化合物 纯金属的 Cu NaCl 乐 0.1 0.1 固/液界面 AH2O 目 甘油 尼龙 LCu/LPb 0.03甲醇 0.03 有机化合物 石蜡 Hg 石蜡/H2O 特弗伦 0.01 0.01 100 300 1000 3000 100 300 1000 3000 熔点，Tm/K 熔点，Tm/K (a)纯物质的表面能 (b)各种界面能 图5.1(a) 固体或液体的表面能（金属最大，塑料最小）；(b)固/液或 液/液界面能和随机晶界能（因物质组合的不同而变得多种多样）
Surface energy of materials
上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Approximate Calculation of Solid Surface Energy(1) The binding energy of an atom to a solid is the result of discrete bonds to its nearest neighbors,then the energy of one bond,s,can be written as follows: △Hs S= 0.5ZNA AHs The molar enthalpy of sublimation (breaking all the bonds) Z The coordination number N,Avogadro's number There are 0.5ZNA bonds per mole
Approximate Calculation of Solid Surface Energy (1)
上浒充通大粤 SHANGHAI JIAO TONG UNIVERSITY Approximate Calculation of Solid Surface Energy (2) If we cleave a face-centered cubic crystal along a(111)plane,three bonds per atom will be broken.Two surfaces formed,the work required to form the surfaces will be 38/2 per surface atom. 3 W= △Hs V6/4a (for Z=12) △Hs E 2 ANA 0.5ZN4 △Hs Y= v2/2ao 4N, aov 2 N/A is the number of atoms per unit (Face diagonal) area.For fec structure: Figure 4.2 Atomic packing on the (111)face of a face-centered N 4 cubic crystal. A 2,* A/N= a=3a2 4 4
Approximate Calculation of Solid Surface Energy （2）