Introduction(2) S.J.T.U. Phase Transformation and Applications Page 6/42 Surface energy based on Gibbs free energy dG =-SaT +VdP ydA aG OH OF aA T.P A )sy S.P A 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. SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 20 surfacePhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 20 surface Page 6/42 Introduction (2) Surface energy based on Gibbs free energy = − + + γdAVdPSdTdG A PT G , ⎟⎠⎞ ⎜⎝⎛ ∂∂ γ = 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. PT VS PS A VT F A H A U A G , , , , ⎟⎠⎞ ⎜⎝⎛ ∂∂ ⎟ = ⎠⎞ ⎜⎝⎛ ∂∂ ⎟ = ⎠⎞ ⎜⎝⎛ ∂∂ ⎟ = ⎠⎞ ⎜⎝⎛ ∂∂ γ =