ABSTRACT CTS-9706805 Univ. of Rochester Fundamental aspects of the critical behavior of a confined fluid in a model nanoscale pore structure are being investigated utilizing finite-size scaling theory in conjunction with computer simulation methodology. Original results are described for analyzing critical phenomena in there types of systems. The framework developed incorporates critical scaling concepts and rigorously accounts for finite-size effects that are important when doing simulations in the critical region. Underpinning the analysis in the confined system has been the assumption of universality between the gas-liquid and Ising-type systems, a perspective in keeping with the results of modern critical phenomena theory. The finite-size scaling analysis presented leads to very specific conditions that define the onset of critical behavior, and hence the phase transition regime, in the confined system. In this way, size dependence is made an ally of the simulations and helps lead to novel methods for predicting critical properties and other fundamental behavior of interest in these systems. Understanding the thermodynamic and transport behavior of near-critical fluids confined in porous substrates is important to several areas of research in chemical and materials engineering. These include the development of methods for using porous materials to efficiently store gases with low bulk critical temperatures, metallic thin film deposition in porous media using supercritical fluid chemical vapor deposition (SFCVD) and the use of supercritical fluids for drying porous silicon and aerogels. In this latter application, the drying trajectory of the process is chosen to expressly avoid traversing the intrapore fluid's phase boundary.
