Investigation Of The Critical Crossover Phenomena In Several Complex Systems

The coexistence curves and light scattering data for a critical solution of benzonitrile + octane have been reported. The critical exponents relating to the difference in the density variables between two coexisting phasesβ, the osmotic compressibilityγ, and the correlation length v have been deduced and the values were consistent with the 3D-Ising value in the range close to the critical point. The experimental results of the coexistence curves have also been analyzed to examine the Wegner correction terms and the behavior of the diameter of the coexistence curves. The light scattering data were well described by the crossover model proposed by Anisimov and Sengers, and showed a monotonic crossover of the critical exponentsγand v from their 3D-Ising values to the mean-field values as the temperature departed from the critical point. Furthermore, the dependences of the critical amplitudes on the mass of n-alkane for the binary solutions of (benzonitrile+n-alkane) have been discussed.The critical phenomena of critical mixture H₂O+3-methylpyridine+sodium bromide have been studied by the dynamic and static light scattering measurements. The dynamic correlation length and the static correlation length were measured and found to be consistent with each other. Moreover, the dynamic and static effective critical exponents exhibited the 3D-Ising value and no crossover was observed in the temperature range we studied.The coexistence curves and light scattering data for a critical solution of 2,6-dimethypyridine+H₂O have been reported. The critical exponents relating to the difference in the density variables between two coexisting phasesβ, the osmotic compressibilityγ, and the correlation lengthÏ…have been deduced. The light scattering data were well described by the crossover model proposed by Anisimov and Sengers, and the effective critical exponentsγandÏ…showed nonmonotonic crossovers from the 3D-Ising values to the mean-field ones as the temperature departed from the critical point. The coexistence curves exhibited that the values of effective critical exponents for the order parameters of refractive-index and the volume fraction decreased while that for the mole fraction increased as the distance from the critical point increased, However, all of the three variables exhibit nonmonotonic crossovers from 0.328 to 0.4 after the regular terms are subtracted.The coexistence curves and light scattering data for a series of critical solutions Of H₂O+2,6-dimethypyridine+sodium bromide have been reported. The critical exponents relating to the difference in the density variables between two coexisting phasesβ, the osmotic compressibilityγ, and the correlation length v have been deduced. The light scattering data were well described by the crossover model proposed by Anisimov and Sengers, and the effective critical exponentsγandÏ…showed nonmonotonic crossovers from the 3D-Ising values to the mean-field ones as the temperature departed from the critical point. The coexistence curves exhibited that the values of effective critical exponents for the order parameter of the refractive-index decreased as the distance from the critical point increased, however after the regular terms were subtracted, the nonmonotonic crossovers from Ising to mean-field critical behavior were exhibited. The influence of sodium bromide on the trend of the crossover was small.The critical crossover behavior in the ternary electrolyte solutions of water +ethanol+potassium carbonate have been studied by measurements of refractive indexes in two coexisting phases. The effective critical exponents were similar to thatof the Flory model. However, afterÏ„_UL was chosen as the field variable in analysisof the closed loops of coexistence curves with both upper and lower critical points, the monotonic crossover from Ising to mean-field critical behavior was exhibited.