HEAT OF FUSION AND SURFACE-TENSION OF SOLIDS CONFINED IN POROUS MATERIALS DERIVED FROM A COMBINED USE OF NMR AND CALORIMETRY

Assuming the heat of fusion (Delta h(f)) of a material confined in a p orous material to be approximated by a function Delta h(f) = Delta h(0 ) (1 + a(0)(10(3)/T) + a(1)(10(3)/T)(2)), where T is the absolute temp erature, a theoretical model is derived that enables the coefficients a(i) to be determined from a combined use of NMR and calorimetric meas urements. The model has been applied on solid ice confined in cement p astes resulting in a(0) = -0.136 K and a(1) = -0.00413 K-2 in the temp erature range 273 K > T > 210 K. Delta h(0) was determined from the kn own value of Delta h(f) of bulk water at 273 K, giving Delta h(0) = 74 9 J/g. Likewise, assuming the surface tension (gamma) of the ice-water interface to be approximated by a corresponding second-order polynomi al in 1/T, i.e., gamma = gamma(0) (1 + b(0)(10(3)/T) + b(1)(10(3)/T)(2 )), the coefficients b(i) were determined from the Gibbs-Thomson equat ion: Delta T = K-f(gamma/rho Delta h(f))(1/R), where K-f is a constant , rho the density, and Delta T the lowering of the melting point of ic e confined in pores with radius R. The model fit revealed a best fit t o a linear function in 1/T, with b(1) = 0 and b(0) = -(0.114 +/- 0.033 ) K. The gamma(0) was determined from the known value of gamma at 273 K, resulting in gamma(0) = 130 erg/cm.