Basic models for collision controlled reactions in the gas phase, as well as models of evaporation have been developed over the past century and incorporated into nanoparticle growth models. However, there are a number of features of nanocluster and nanoparticle formation and growth processes which are often omitted in models and require further investigation to be properly considered. Specifically, (1) the influence of nanocluster structure on their transport and growth, (2) the influence of nanocluster-nanocluster (or nanoparticle-nanoparticle) interactions on collision controlled reactions, (3) the dissociation rates and stability of nanoclusters, whose properties may deviate from bulk matter, and (4) appropriate methods to link growth rate equations to the evolution of nanocluster/nanoparticle size distribution all must be considered in growth models. Typically, these features are either omitted or accounted for with simple approximations, not because they are not important, but because they are poorly understood. This dissertation focuses on these four topics, with the specific studies carried out in each chapter. Each of the four studies contains their own introduction, methods, results & discussion, and conclusion sections, and each is intended to serve as a stand-alone contribution to the study of nanocluster/nanoparticle transport and growth in the gas phase. At the same time, all studies are related to the evaluation of nanocluster/nanoparticle properties which can be inputs into growth and transport models for atmospheric and high temperature aerosols.