Aerogels, description

The strongly density-dependent factor G considers the effects of the ineffective dead ends of the solid backbone, the increase in the specific heat due to the enhanced specific surface of an aerogel, the meandering chains along a temperatme gradient and the constriction of heat flow at the connecting area between the primary particles within the chains. A proper approach to the description of the density dependence is provided by the... 

The physical-mathematical description of the heat transfer in optically thin aerogels leads to coupled nonlinear integrodifferential equations which cannot be treated analytically. In the heat transfer equation, (23.1), the heat source term O considers the net radiative heat flux into the infinitesimal volume element where this equation is defined ... 

More recently, different approaches (cellular models, percolation analogy, fractal structure, blobs and links) have been proposed, to account for the porous volume and calculate the evolution of the meehanical properties as a function of the structural characteristics. Such models seem attraetive to deseribe the meehanieal properties of gels for several reasons. In eontrast with the empirieal relationships, they try to relate the physieal properties to a description of the mean strueture, or to the aggregation process they also predict that the Poisson ratio is with the fraetion of the solid phase, which is an experimental result demonstrated for aerogels and PDA. Another interesting feature of those models is that they prediet a power law evolution of the meehanieal properties as a funetion of the... 

Acetylene-substituted Si-N-P compounds, synthesis, 236-237 Activated aluminas, description, 165 Aerogels, definition, 127 Aggregation of fractals, 104,106 Alcohol-substituted polymers from aldehydes and ketones, deprotonation-substitution reactions, 249-250 Alkenylborazine copolymers, quantitative reactivity studies of copolymerization reactions, 394... 

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