Variation of vapor pressure with particle size S.J.T.U. Phase Transformation and Applications The pressure on a small droplet is the sum of the imposed gas pressure and the internal pressure generated by the surface tension of the material 2mrY=2△p 2Y A= ViPr RTIn Figure 4.7 The force holding two hemispheres together is 2mry:the force pushing them apart is mAP. where△P=2ylr. r) The vapor pressure above the small particles is greater than the vapor pressure In- 2Y above the large particles.Material would RT then move through the gas phase from small particles to larger ones.Coarsening SJTU Thermodynamics of Materials Spring 2006 ©X.J.Jin ecture 9 Chemical equilibrium IlPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Lecture 9 Chemical equilibrium II Variation of vapor pressure with particle size The pressure on a small droplet is the sum of the imposed gas pressure and the internal pressure generated by the surface tension of the material Δ= prr 2 2 πγπ r p 2γ =Δ e Tl RTpV π π = ln e l RT r V π γ π ln 2 ⎟ =⎠⎞ ⎜⎝⎛ ⎟⎠⎞ ⎜⎝⎛ = rRTV l e γ ππ 2 ln The vapor pressure above the small particles is greater than the vapor pressure above the large particles. Material would then move through the gas phase from small particles to larger ones. Coarsening